Synergy is the main point for a team's success. Synergy can be defined as two pokemon resisting each other's weaknesses and two pokemon able to take out all the 17 types in pokemon.
Without further ado , I present you the team :
Gengar @ Wide Lens
Timid Nature
Levitate
4 HP / 252 Speed / 252 Special Attack
- Hypnosis
- Destiny Bond
- Focus Blast
- Shadow Ball
The first member of my team . Gengar serves a very important role in the team. First , it sleeps the lead. After Wide Lens, the significant increase in accuracy of its moves, Hypnosis and Focus Blast respectively , will help Gengar alot. Hypnosis is the first move I use most of the time to sleep leads. With 350 Speed , Gengar finds no problem trying to outspeed leads . Leads that Gengar are unable to outspeed include Crobat,Azelf and Aerodactyl,which I have counters for. Destiny Bond is to take down a pokemon together with it ,specifically Scizor. Scizor tends to use PURSUIT instead of BULLET PUNCH to hit Gengar , as they expect me to switch out . This is one scenario when Destiny Bond works wonders . Focus Blast helps me hit most leads , namely Metagross,Abomasnow,Lucario,Infernape,etc,after hypnotising them to sleep. Shadow Ball is the obligatory STAB move and gains perfect coverage with Focus Blast , hitting every pokemon in the OU tier for at least neutral damage.Let us take a look at how Gengar handles the common leads :
Azelf - Hypnosis on turn one to check if it has Taunt . If it has no Taunt , continue Shadow Balling it to death after hypnotizing it.Otherwise , switch out to the appropriate counter.
Aerodactyl - Shadow Ball straight as the chance of Aerodactyl not running Taunt is less than 1%. If needed,switch out to appropriate counter.
Metagross - Hypnosis it to sleep and proceed to hit it with Shadow Ball or Focus Blast. The most it can do is Bullet Punch me(if it uses it on Turn One).
Ninjask - Easiest match-up. Break its Substitutes with Shadow Ball and Hypnosis the switch-in when it Baton Passes its boosts without a Substitute when it has no HP left.
Lucario - Hypnosis on turn one and Focus Blast + Shadow Ball for the OHKO , should it have Focus Sash. Otherwise, Focus Blast does the job.
Tyranitar - Hypnosis on turn one to be safe if Focus Blast does not OHKO on Turn two.
Hippowdon - Sleep it with Hypnosis and switch out.
Abomasnow - No need to sleep it , Focus Blast it to oblivion of the North Pole.
Infernape - Sleep it with Hypnosis and continue to hit it with 2 Shadow Balls after Focus Sash.
As you can see, Gengar handles most leads easily.Gengar serves as my spin blocker late game as well,should it be able to survive.
[Synergy]
Blocks Rapid Spin
Prevents entry hazards most of the time
Cripple a pokemon
Counters Blissey
Takes Fighting moves
Takes Normal moves
Takes Ground moves
Takes Grass moves
Takes Bug moves
Takes Poison moves
Takes Toxic and Will-o-Wisp
No damage from Spikes
No effect from Toxic Spikes
Skarmory @ Leftovers
Careful Nature
Keen Eye
252 HP / 4 Defense / 252 Special Defense
- Brave Bird
- Stealth Rock
- Roost
- Roar
Skarmory serves as my standard phazer and wall. Stealth Rock is the obligatory move on Skarmory which may turn 2HKOs into OHKOs , and 3HKOs into 2HKOs. Roost is the recovery move on Skarmory which removes its Electric weakness. Roar enables me to scout the opponent's team. Skarmory is able to take 2 Close Combats from Pinsir ( 125 Attack , STABed ) and 1 Head Smash from Aggron ( Choice Band ) , while I Roost , causing Head Smash to be ineffective. Skarmory is your standard one and I think this explanation should be enough . The EVs allow it to wall from both sides of the spectrum.
[Synergy]
Takes most physical hits like a champ
Phazes away stat uppers
Sets up Stealth Rock
Walls Head Smash Aggron
Takes Normal moves
Takes Dark moves
Takes Grass moves
Takes Ghost moves
Takes Ground moves
Takes Bug moves
Takes Steel moves
Takes Poison moves
Takes Dragon moves
Takes Toxic
Absorbs Thunder Wave
Resists all of Latias's and Kingdra's weaknesses
No damage from Spikes
No effect from Toxic Spikes
Latias @ Life Orb
Bold Nature
Levitate
252 HP / 252 Def / 4 Spe
- Thunder Wave
- Recover
- Dragon Pulse
- Charge Beam
My own variant of Latias. Physically oriented to take one U-Turn from Scizor(max 80% iirc) from CB Scizor. Thunder Wave paralyses foes and makes up for the lack of 248 EVs in Speed. Recover to negate Life Orb damage. Charge Beam serves as Calm Mind , but it does damage. Dragon Pulse as the STAB move that has the same power as a +0 Draco Meteor after one Charge Beam boost. Dragon Pulse and Charge Beam,if I am not wrong,has perfect coverage together. Latias finds no problem trying to survive a +0 Outrage / Draco Meteor from Salamence, Dragonite or Flygon without Choice Band whilst it OHKOs with Dragon Pulse should they not be Specially Defensive oriented. Dragonite may survive,though. This variant of Latias easily breaks stall as it is capable of 2HKOing Blissey after Stealth Rock and prior damage with Dragon Pulse. It does a minimum of 39.5% damage to max HP / max SDef +Nature Blissey that is only prominent in Ubers. In OU,it is max HP / max Def neutral Nature,therefore it does a minimum of 52.2% damage , capable of OHKOing it out if it has taken 36% of damage beforehand excluding Stealth Rock. If there is a Critical hit , it is OHKOed before prior damage + Stealth Rock. Latias is a very important member of the team.
[Synergy]
Takes Will-o-Wisp
Spreads paralysis
Can stall Blissey out
Takes Psychic moves
Takes Fighting moves
Takes Ground moves
Takes Fire moves
Takes Water moves
Takes Grass moves
Takes Electric moves
No damage from Spikes
No effect from Toxic Spikes
Resists all of Empoleon's and Skarmory's weaknesses
Empoleon @ Petaya Berry
Modest Nature
Torrent
12 HP / 8 Def / 236 Spe / 252 SAtk
- Substitute
- Agility
- Hidden Power [ Dragon ] / Grass Knot / Ice Beam Ice Beam
- Surf
Empoleon,the world's most famous and the best special sweeper. Agility + Substitute + Petaya Berry. The best and infamous set of Empoleon. With Agility , Empoleon reaches 430 Speed iirc,outspeeding all base 90 scarfers.
Surf is the STAB move that reaches 137.5 power before Torrent activates which easy wipes out all pokemon should Petaya Berry and Torrent be activated.It does ~70% to Salamence IIRC.As for the 3rd moveslot , I am having troubles with.If I run Hidden Power [ Dragon ] , I can hit all Grass,Dragons and Waters, who resist Surf. If I run Grass Knot, I hit the Waters only.If I run Ice Beam,I hit the Grasses and Dragons only.But,the power difference,between Hidden Power [ Dragon ] and Ice Beam is 25 , a significant difference , if you count in Petaya Berry. Therefore, I need some suggestions on what move to use.The EVs allow 312 HP, enough to set up 3 Substitutes and for the Petaya Berry to activate. 236 Spe allows me to reach 430 Speed and max SpAtk to maximize power.I am not sure why the 8 Def EVs are there.I have went with Ice Beam to take down DDing Mence after 1 Agility.
[Synergy]
Outspeed Scarfers base 90s after one Agility
Able to OHKO Head Smash Aggron ( CB , Stuck in Head Smash ) .
Takes Normal moves
Takes Ice moves
Takes Dragon moves
Takes Dark moves
Takes Ghost moves
Takes Bug moves
Takes Poison moves
Takes Flying moves
Takes Rock moves
Takes Water moves
No effect from Toxic Spikes
Absorbs Toxic
Resists all the weaknesses of Latias and Kingdra
Electivire @ Expert Belt
Naive Nature
Motor Drive
188 Attack / 252 Speed / 68 Special Attack
- Cross Chop
- Ice Punch
- Thunderbolt
- Earthquake / Fire Punch
Electivire absorbs Electric attacks for the team , and uses it for a nice Speed boost . Cross Chop hits Blissey for Super Effective damage and with a nice boost from Expert Belt , OHKOing max HP / max Def +Nature IIRC.Thunderbolt OHKOs Skarmory and is something that Thunderpunch cannot do. Earthquake hits Jolteons and other Electric types , but Fire Punch hits Scizor. It is very hard to choose between these two as my team is slightly Scizor weak. I need suggestions on this. Electivire gains perfect coverage with the moves, hitting every pokemon for neutral damage and Expert Belt is a good item as most pokemon get hit for Super Effective damage,lest Neutral damage.The EVs allow max Speed,and the rest are just pumped into Attack and Special Attack.
[Synergy]
Has Super Effective on more than 10 of the 17 types
Uses Electric moves to its advantage
Mixed Sweeper
Takes Electric moves
Takes Steel moves
(>,< not really much but his ability to hit Super Effective on most types make up for this)
Kingdra @ Lum Berry
Adamant Nature,
Swift Swim
4 HP / 252 Attack / 252 Speed
- Dragon Dance
- Waterfall
- Outrage
- Substitute
SubDD Kingdra is a beast when it gets to set up. Able to deal 38% damage(Waterfall) to Salamence after +1 not counting in Intimidate is a great deal if it switches in.Kingdra is also able to outspeed Scarf Latias after +2 Speed. Substitute is the main gist of the set.Switching in on a Water-typed move or tank,namely Forretress,Blissey, and set up Substitute. Forretress can only use Explosion to hit me as Gyro Ball does not break my Sub before 1 Speed boost.Blissey can only use Seismic Toss to break my Subs but most Blissey run DoubleStatus + Softboiled + Ice Beam / Thunderbolt nowadays. Therefore , Kingdra finds many opportunies to set up with only 1 weakness and 95/95/95 defenses . Dragon Dance allows Kingdra to sweep more effectively , boosting its Attack and Speed. Waterfall and Outrage provides me with perfect coverage. Kingdra is also my Rain team counter with Swift Swim.Lum Berry negates the Confusion from Outrage and allows it to attack more effectively. The EVs are the standard EVs.
[Synergy]
Takes Fire moves
Takes Steel moves
Takes Water moves
Overall Weakness / Resistant / Immunity Chart :
Weaknesses
Normal - 0
Grass - 0
Electric - 2
Dragon - 2
Ice - 2
Water - 0
Ghost - 1
Dark - 1
Bug - 1
Poison - 0
Ground - 2
Rock - 0
Flying - 0
Fire - 1
Steel - 0
Fighting - 1
Psychic - 1
Resistances
Normal - 2
Electric - 1
Water - 3
Grass - 3
Fire - 2
Ground - 0
Dragon - 2
Fire - 2
Poison - 0
Dark - 2
Ghost - 2
Steel - 4
Flying - 3
Rock - 1
Bug - 3
Ice - 1
Fighting - 1
Immunity
Normal - 1
Fighting - 1
Poison - 4
Bug - 0
Fire - 0
Electric - 1
Water - 0
Ground - 3
Dragon - 0
Steel - 0
Water - 0
Grass - 0
Flying - 0
Ice - 0
Rock - 0
Dark - 0
Ghost - 0
There you go , my synergy team . I am particularly short of Ice resistances now as I have one Pokemon only ( Empoleon ) who resists Ice.
Without further ado , I present you the team :

Gengar @ Wide Lens
Timid Nature
Levitate
4 HP / 252 Speed / 252 Special Attack
- Hypnosis
- Destiny Bond
- Focus Blast
- Shadow Ball
The first member of my team . Gengar serves a very important role in the team. First , it sleeps the lead. After Wide Lens, the significant increase in accuracy of its moves, Hypnosis and Focus Blast respectively , will help Gengar alot. Hypnosis is the first move I use most of the time to sleep leads. With 350 Speed , Gengar finds no problem trying to outspeed leads . Leads that Gengar are unable to outspeed include Crobat,Azelf and Aerodactyl,which I have counters for. Destiny Bond is to take down a pokemon together with it ,specifically Scizor. Scizor tends to use PURSUIT instead of BULLET PUNCH to hit Gengar , as they expect me to switch out . This is one scenario when Destiny Bond works wonders . Focus Blast helps me hit most leads , namely Metagross,Abomasnow,Lucario,Infernape,etc,after hypnotising them to sleep. Shadow Ball is the obligatory STAB move and gains perfect coverage with Focus Blast , hitting every pokemon in the OU tier for at least neutral damage.Let us take a look at how Gengar handles the common leads :
Azelf - Hypnosis on turn one to check if it has Taunt . If it has no Taunt , continue Shadow Balling it to death after hypnotizing it.Otherwise , switch out to the appropriate counter.
Aerodactyl - Shadow Ball straight as the chance of Aerodactyl not running Taunt is less than 1%. If needed,switch out to appropriate counter.
Metagross - Hypnosis it to sleep and proceed to hit it with Shadow Ball or Focus Blast. The most it can do is Bullet Punch me(if it uses it on Turn One).
Ninjask - Easiest match-up. Break its Substitutes with Shadow Ball and Hypnosis the switch-in when it Baton Passes its boosts without a Substitute when it has no HP left.
Lucario - Hypnosis on turn one and Focus Blast + Shadow Ball for the OHKO , should it have Focus Sash. Otherwise, Focus Blast does the job.
Tyranitar - Hypnosis on turn one to be safe if Focus Blast does not OHKO on Turn two.
Hippowdon - Sleep it with Hypnosis and switch out.
Abomasnow - No need to sleep it , Focus Blast it to oblivion of the North Pole.
Infernape - Sleep it with Hypnosis and continue to hit it with 2 Shadow Balls after Focus Sash.
As you can see, Gengar handles most leads easily.Gengar serves as my spin blocker late game as well,should it be able to survive.
[Synergy]
Blocks Rapid Spin
Prevents entry hazards most of the time
Cripple a pokemon
Counters Blissey
Takes Fighting moves
Takes Normal moves
Takes Ground moves
Takes Grass moves
Takes Bug moves
Takes Poison moves
Takes Toxic and Will-o-Wisp
No damage from Spikes
No effect from Toxic Spikes

Skarmory @ Leftovers
Careful Nature
Keen Eye
252 HP / 4 Defense / 252 Special Defense
- Brave Bird
- Stealth Rock
- Roost
- Roar
Skarmory serves as my standard phazer and wall. Stealth Rock is the obligatory move on Skarmory which may turn 2HKOs into OHKOs , and 3HKOs into 2HKOs. Roost is the recovery move on Skarmory which removes its Electric weakness. Roar enables me to scout the opponent's team. Skarmory is able to take 2 Close Combats from Pinsir ( 125 Attack , STABed ) and 1 Head Smash from Aggron ( Choice Band ) , while I Roost , causing Head Smash to be ineffective. Skarmory is your standard one and I think this explanation should be enough . The EVs allow it to wall from both sides of the spectrum.
[Synergy]
Takes most physical hits like a champ
Phazes away stat uppers
Sets up Stealth Rock
Walls Head Smash Aggron
Takes Normal moves
Takes Dark moves
Takes Grass moves
Takes Ghost moves
Takes Ground moves
Takes Bug moves
Takes Steel moves
Takes Poison moves
Takes Dragon moves
Takes Toxic
Absorbs Thunder Wave
Resists all of Latias's and Kingdra's weaknesses
No damage from Spikes
No effect from Toxic Spikes

Latias @ Life Orb
Bold Nature
Levitate
252 HP / 252 Def / 4 Spe
- Thunder Wave
- Recover
- Dragon Pulse
- Charge Beam
My own variant of Latias. Physically oriented to take one U-Turn from Scizor(max 80% iirc) from CB Scizor. Thunder Wave paralyses foes and makes up for the lack of 248 EVs in Speed. Recover to negate Life Orb damage. Charge Beam serves as Calm Mind , but it does damage. Dragon Pulse as the STAB move that has the same power as a +0 Draco Meteor after one Charge Beam boost. Dragon Pulse and Charge Beam,if I am not wrong,has perfect coverage together. Latias finds no problem trying to survive a +0 Outrage / Draco Meteor from Salamence, Dragonite or Flygon without Choice Band whilst it OHKOs with Dragon Pulse should they not be Specially Defensive oriented. Dragonite may survive,though. This variant of Latias easily breaks stall as it is capable of 2HKOing Blissey after Stealth Rock and prior damage with Dragon Pulse. It does a minimum of 39.5% damage to max HP / max SDef +Nature Blissey that is only prominent in Ubers. In OU,it is max HP / max Def neutral Nature,therefore it does a minimum of 52.2% damage , capable of OHKOing it out if it has taken 36% of damage beforehand excluding Stealth Rock. If there is a Critical hit , it is OHKOed before prior damage + Stealth Rock. Latias is a very important member of the team.
[Synergy]
Takes Will-o-Wisp
Spreads paralysis
Can stall Blissey out
Takes Psychic moves
Takes Fighting moves
Takes Ground moves
Takes Fire moves
Takes Water moves
Takes Grass moves
Takes Electric moves
No damage from Spikes
No effect from Toxic Spikes
Resists all of Empoleon's and Skarmory's weaknesses

Empoleon @ Petaya Berry
Modest Nature
Torrent
12 HP / 8 Def / 236 Spe / 252 SAtk
- Substitute
- Agility
- Hidden Power [ Dragon ] / Grass Knot / Ice Beam Ice Beam
- Surf
Empoleon,the world's most famous and the best special sweeper. Agility + Substitute + Petaya Berry. The best and infamous set of Empoleon. With Agility , Empoleon reaches 430 Speed iirc,outspeeding all base 90 scarfers.
Surf is the STAB move that reaches 137.5 power before Torrent activates which easy wipes out all pokemon should Petaya Berry and Torrent be activated.It does ~70% to Salamence IIRC.As for the 3rd moveslot , I am having troubles with.If I run Hidden Power [ Dragon ] , I can hit all Grass,Dragons and Waters, who resist Surf. If I run Grass Knot, I hit the Waters only.If I run Ice Beam,I hit the Grasses and Dragons only.But,the power difference,between Hidden Power [ Dragon ] and Ice Beam is 25 , a significant difference , if you count in Petaya Berry. Therefore, I need some suggestions on what move to use.The EVs allow 312 HP, enough to set up 3 Substitutes and for the Petaya Berry to activate. 236 Spe allows me to reach 430 Speed and max SpAtk to maximize power.I am not sure why the 8 Def EVs are there.I have went with Ice Beam to take down DDing Mence after 1 Agility.
[Synergy]
Outspeed Scarfers base 90s after one Agility
Able to OHKO Head Smash Aggron ( CB , Stuck in Head Smash ) .
Takes Normal moves
Takes Ice moves
Takes Dragon moves
Takes Dark moves
Takes Ghost moves
Takes Bug moves
Takes Poison moves
Takes Flying moves
Takes Rock moves
Takes Water moves
No effect from Toxic Spikes
Absorbs Toxic
Resists all the weaknesses of Latias and Kingdra

Electivire @ Expert Belt
Naive Nature
Motor Drive
188 Attack / 252 Speed / 68 Special Attack
- Cross Chop
- Ice Punch
- Thunderbolt
- Earthquake / Fire Punch
Electivire absorbs Electric attacks for the team , and uses it for a nice Speed boost . Cross Chop hits Blissey for Super Effective damage and with a nice boost from Expert Belt , OHKOing max HP / max Def +Nature IIRC.Thunderbolt OHKOs Skarmory and is something that Thunderpunch cannot do. Earthquake hits Jolteons and other Electric types , but Fire Punch hits Scizor. It is very hard to choose between these two as my team is slightly Scizor weak. I need suggestions on this. Electivire gains perfect coverage with the moves, hitting every pokemon for neutral damage and Expert Belt is a good item as most pokemon get hit for Super Effective damage,lest Neutral damage.The EVs allow max Speed,and the rest are just pumped into Attack and Special Attack.
[Synergy]
Has Super Effective on more than 10 of the 17 types
Uses Electric moves to its advantage
Mixed Sweeper
Takes Electric moves
Takes Steel moves
(>,< not really much but his ability to hit Super Effective on most types make up for this)

Kingdra @ Lum Berry
Adamant Nature,
Swift Swim
4 HP / 252 Attack / 252 Speed
- Dragon Dance
- Waterfall
- Outrage
- Substitute
SubDD Kingdra is a beast when it gets to set up. Able to deal 38% damage(Waterfall) to Salamence after +1 not counting in Intimidate is a great deal if it switches in.Kingdra is also able to outspeed Scarf Latias after +2 Speed. Substitute is the main gist of the set.Switching in on a Water-typed move or tank,namely Forretress,Blissey, and set up Substitute. Forretress can only use Explosion to hit me as Gyro Ball does not break my Sub before 1 Speed boost.Blissey can only use Seismic Toss to break my Subs but most Blissey run DoubleStatus + Softboiled + Ice Beam / Thunderbolt nowadays. Therefore , Kingdra finds many opportunies to set up with only 1 weakness and 95/95/95 defenses . Dragon Dance allows Kingdra to sweep more effectively , boosting its Attack and Speed. Waterfall and Outrage provides me with perfect coverage. Kingdra is also my Rain team counter with Swift Swim.Lum Berry negates the Confusion from Outrage and allows it to attack more effectively. The EVs are the standard EVs.
[Synergy]
Takes Fire moves
Takes Steel moves
Takes Water moves
Overall Weakness / Resistant / Immunity Chart :
Weaknesses
Normal - 0
Grass - 0
Electric - 2
Dragon - 2
Ice - 2
Water - 0
Ghost - 1
Dark - 1
Bug - 1
Poison - 0
Ground - 2
Rock - 0
Flying - 0
Fire - 1
Steel - 0
Fighting - 1
Psychic - 1
Resistances
Normal - 2
Electric - 1
Water - 3
Grass - 3
Fire - 2
Ground - 0
Dragon - 2
Fire - 2
Poison - 0
Dark - 2
Ghost - 2
Steel - 4
Flying - 3
Rock - 1
Bug - 3
Ice - 1
Fighting - 1
Immunity
Normal - 1
Fighting - 1
Poison - 4
Bug - 0
Fire - 0
Electric - 1
Water - 0
Ground - 3
Dragon - 0
Steel - 0
Water - 0
Grass - 0
Flying - 0
Ice - 0
Rock - 0
Dark - 0
Ghost - 0
There you go , my synergy team . I am particularly short of Ice resistances now as I have one Pokemon only ( Empoleon ) who resists Ice.