This team is a team made for Double Battles, and is based around the ability Justified. First Pokemon is Whimsicott, which is the key to making this happen.
Whimsicott
Prankster @ Leftovers
Moves:
-Beat Up
-Stun Spore
-Leech Seed
-Substitute
Nature: Bold
EVs: 252 HP / 252 Def / 4 SpD
Sure you might be thinking that just because he has no speed EVs that this is ineffective. Well, there is a point behind it, and that is giving Terrakion some time to set up with Stealth Rock. This set is used to not only boost my Justified users, but also support them by Paralyzing their enemies, which is also useful for Gallade, due to his disappointing speed stat. Leech Seed and Substitute are to whittle down the opponents that aren't killed by one shot of Rock Slide. This set isn't perfect, but it suits my needs.
Terrakion
Justified @ Leftovers
Moves:
-Rock Slide
-Close Combat
-Stealth Rock
-X-Scissor
Nature: Jolly
EVs: 4 HP / 252 Atk / 252 Spe
Terrakion is probably the best sweeper in this team. Terrakion has great defense, attack, and is blistering fast. He also is the only one in this team that receives STAB to the main part of this team which is Rock Slide. X-Scissor is mainly for coverage, and Stealth Rock is used to also whittle down any enemy that isn't killed in one hit from the boosted beast. Close Combat, I chose just as another good STAB move and is used to counter annoying Steel types that aren't affected as much by his Rock Slide.
Gallade
Justified @ Choice Scarf/Expert Belt
Moves:
-Rock Slide
-Drain Punch
-Ice Punch
-Shadow Sneak
Nature: Jolly
EVs: 4 HP / 252 Atk / 252 Spe
Gallade is another of my Justified sweepers. Unfortunately, Gallade has disappointing speed, so to solve that problem, I gave him a choice scarf and gave Whimsicott Stun Spore. Rock Slide is the main basis of the set, and is to take on the double battle terrain. Drain Punch, is it's main means of recovery and is also a STAB move. I also gave it two coverage moves in Shadow Sneak and Ice Punch taking out its only two weaknesses in Ghost and Flying. If you prefer to rely soley on Stun Spore to ensure Gallade gets the required speed to sweep, you can use an Expert Belt instead to give it a boost on it's Super Effective moves
Cobalion
Justified @ Leftovers
Moves:
-Stone Edge
-Iron Head
-Stealth Rock
-Close Combat
Nature: Jolly
EVs: 4 HP / 252 Atk / 252 Spe
While Cobalion, unfortunately, does not come equipped with Rock Slide, I chose him due to his great Defense, and a ton of resistances. I chose Stone Edge to deal massive damage and is one of the main moves of the set. I also chose STAB Iron Head due to it's decent power, and a chance for flinch. Stealth Rock is added just in case i want to use Cobalion instead of Terrakion first, mostly depending on the opponents team. Close Combat is another STAB move to this set that deals great damage and barely dents Cobalion's massive Defense stat.
Snorlax
Thick Fat @ Leftovers
Moves:
-Curse
-Earthquake
-Fire Punch
-Body Slam
Nature: Adamant
EVs: 252 HP / 252 Atk / 4 SpD
To ensure that my team isn't stopped by Trick Room teams, or if my Justify users are somehow knocked out, Curselax is the set to fall back on. Since my team heavily relies on hitting first and hard, I decided to slow things down a bit, and also counter any trick room teams with Curse which makes Snorlax bulkier, hit harder, and move faster under trick room. I decided to go with Body Slam over the popular Return due to it's chance at dealing paralysis. Fire Punch is mostly a filler move but also counters annoying Pokemon such as Levitate Bronzong. Earthquake is in this set due to it's great power, and the fact that it hits every Pokemon on the field. Fortunately, Whimsicott and Breloom resist it, and they are both running bulky sets.
Breloom
Poison Heal @ Toxic Orb
Moves:
-Spore
-Substitute
-Focus Punch
-Facade
Nature: Adamant
EVs: 248 HP / 252 Atk / 8 Def
And finally Breloom. Breloom has gained a lot of momentum because of it's new ability Technician. I personally still prefer a Poison Heal Breloom, as it is a lot harder to deal with than Techloom. This set runs under the basis of putting your opponent to sleep, setting up a Substitute, and SubPunching your opponents to death. Also if that isn't enough, Breloom has Facade in this set, which deals insane damage when it is poisoned. Also with the EV spread, Breloom already reaches an insane 394 Attack stat giving it the capability to take down most things in the tier. Unfortunately, Breloom is completely walled by ghosts with this set, but that is covered by Gallade.
Also in case you want to test it out, here is an import spread for PS

Prankster @ Leftovers
Moves:
-Beat Up
-Stun Spore
-Leech Seed
-Substitute
Nature: Bold
EVs: 252 HP / 252 Def / 4 SpD
Sure you might be thinking that just because he has no speed EVs that this is ineffective. Well, there is a point behind it, and that is giving Terrakion some time to set up with Stealth Rock. This set is used to not only boost my Justified users, but also support them by Paralyzing their enemies, which is also useful for Gallade, due to his disappointing speed stat. Leech Seed and Substitute are to whittle down the opponents that aren't killed by one shot of Rock Slide. This set isn't perfect, but it suits my needs.

Justified @ Leftovers
Moves:
-Rock Slide
-Close Combat
-Stealth Rock
-X-Scissor
Nature: Jolly
EVs: 4 HP / 252 Atk / 252 Spe
Terrakion is probably the best sweeper in this team. Terrakion has great defense, attack, and is blistering fast. He also is the only one in this team that receives STAB to the main part of this team which is Rock Slide. X-Scissor is mainly for coverage, and Stealth Rock is used to also whittle down any enemy that isn't killed in one hit from the boosted beast. Close Combat, I chose just as another good STAB move and is used to counter annoying Steel types that aren't affected as much by his Rock Slide.

Justified @ Choice Scarf/Expert Belt
Moves:
-Rock Slide
-Drain Punch
-Ice Punch
-Shadow Sneak
Nature: Jolly
EVs: 4 HP / 252 Atk / 252 Spe
Gallade is another of my Justified sweepers. Unfortunately, Gallade has disappointing speed, so to solve that problem, I gave him a choice scarf and gave Whimsicott Stun Spore. Rock Slide is the main basis of the set, and is to take on the double battle terrain. Drain Punch, is it's main means of recovery and is also a STAB move. I also gave it two coverage moves in Shadow Sneak and Ice Punch taking out its only two weaknesses in Ghost and Flying. If you prefer to rely soley on Stun Spore to ensure Gallade gets the required speed to sweep, you can use an Expert Belt instead to give it a boost on it's Super Effective moves

Justified @ Leftovers
Moves:
-Stone Edge
-Iron Head
-Stealth Rock
-Close Combat
Nature: Jolly
EVs: 4 HP / 252 Atk / 252 Spe
While Cobalion, unfortunately, does not come equipped with Rock Slide, I chose him due to his great Defense, and a ton of resistances. I chose Stone Edge to deal massive damage and is one of the main moves of the set. I also chose STAB Iron Head due to it's decent power, and a chance for flinch. Stealth Rock is added just in case i want to use Cobalion instead of Terrakion first, mostly depending on the opponents team. Close Combat is another STAB move to this set that deals great damage and barely dents Cobalion's massive Defense stat.

Thick Fat @ Leftovers
Moves:
-Curse
-Earthquake
-Fire Punch
-Body Slam
Nature: Adamant
EVs: 252 HP / 252 Atk / 4 SpD
To ensure that my team isn't stopped by Trick Room teams, or if my Justify users are somehow knocked out, Curselax is the set to fall back on. Since my team heavily relies on hitting first and hard, I decided to slow things down a bit, and also counter any trick room teams with Curse which makes Snorlax bulkier, hit harder, and move faster under trick room. I decided to go with Body Slam over the popular Return due to it's chance at dealing paralysis. Fire Punch is mostly a filler move but also counters annoying Pokemon such as Levitate Bronzong. Earthquake is in this set due to it's great power, and the fact that it hits every Pokemon on the field. Fortunately, Whimsicott and Breloom resist it, and they are both running bulky sets.

Poison Heal @ Toxic Orb
Moves:
-Spore
-Substitute
-Focus Punch
-Facade
Nature: Adamant
EVs: 248 HP / 252 Atk / 8 Def
And finally Breloom. Breloom has gained a lot of momentum because of it's new ability Technician. I personally still prefer a Poison Heal Breloom, as it is a lot harder to deal with than Techloom. This set runs under the basis of putting your opponent to sleep, setting up a Substitute, and SubPunching your opponents to death. Also if that isn't enough, Breloom has Facade in this set, which deals insane damage when it is poisoned. Also with the EV spread, Breloom already reaches an insane 394 Attack stat giving it the capability to take down most things in the tier. Unfortunately, Breloom is completely walled by ghosts with this set, but that is covered by Gallade.
Also in case you want to test it out, here is an import spread for PS
Whimsicott @ Leftovers
Trait: Prankster
EVs: 252 HP / 252 Def / 4 SDef
Bold Nature
- Beat Up
- Stun Spore
- Leech Seed
- Substitute
Terrakion @ Leftovers
Trait: Justified
EVs: 252 Atk / 4 SDef / 252 Spd
Jolly Nature
- Rock Slide
- Close Combat
- Stealth Rock
- X-Scissor
Gallade (M) @ Choice Scarf
Trait: Justified
EVs: 252 Atk / 4 SDef / 252 Spd
Jolly Nature
- Rock Slide
- Drain Punch
- Ice Punch
- Shadow Sneak
Cobalion @ Leftovers
Trait: Justified
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature
- Iron Head
- Stone Edge
- Stealth Rock
- Close Combat
Snorlax @ Leftovers
Trait: Thick Fat
EVs: 252 HP / 252 Atk / 4 SDef
Adamant Nature
- Earthquake
- Curse
- Body Slam
- Fire Punch
Breloom @ Toxic Orb
Trait: Poison Heal
EVs: 8 Def / 248 HP / 252 Atk
Adamant Nature
- Facade
- Substitute
- Spore
- Focus Punch