For 2MuchHax :
Aerodactyl-Mega and Gengar were the first two of the team. AoA Aerodactyl-Mega is a really interesting pick and a really nice Revenge Killer in Underused. Stone Edge is its main STAB while Eartquake allows it to hit Steel Types. Aqua Tail is a good way to hit Pokemon like Krookodile, Hippowdon and Gligar while Pursuit allows Aerodactyl-Mega to trap some threats for its teammates. As you can see, Gengar is not Choice Specs because it's probably one of the worst item for it in the current metagame becauses it leaves it really weak to Pursuit users which sucks a lot. Taunt and Will-O-Wisp are a good way to bother Fat Pokemon which is useful for Aerodactyl-Mega that struggles to break fat core. Hex hits really hard thanks to WoW and Spooky Plate while Sludge Wave is a really good way to punish Fairy Types. Then we have the mighty Empoleon / Hippowdon core which is super good in Underused. I opted for Roar on Empoleon because Hippowdon needs Fire Fang to deal with Scizor which is super threatening for the team otherwise. Roost Hydreigon is a really good Pokemon and a great answer to Crawdaunt, Volcanion or Bisharp to a smaller extent. Taunt and Darkinium Z allow it to weaken Fat Pokemon for Aerodactyl-Mega as well as OHKO Scizor. Finally, Rest-Talk Primarina is a good way to check Hydreigon and Simiabraz and bring some useful Bulk to the team.
That's all, I hope you will like the team
Aerodactyl-Mega @ Aerodactylite
Ability: Tough Claws
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Stone Edge
- Earthquake
- Aqua Tail
- Pursuit
Gengar @ Spooky Plate
Ability: Cursed Body
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Taunt
- Will-O-Wisp
- Hex
- Sludge Wave
Empoleon @ Leftovers
Ability: Torrent
EVs: 248 HP / 76 Def / 184 SpD
Calm Nature
IVs: 0 Atk
- Defog
- Roar
- Toxic
- Scald
Hippowdon @ Rocky Helmet
Ability: Sand Stream
EVs: 248 HP / 84 Def / 176 SpD
Impish Nature
- Stealth Rock
- Slack Off
- Earthquake
- Fire Fang
Hydreigon @ Darkinium Z
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Roost
- Taunt
- Dark Pulse
- Draco Meteor
Primarina @ Leftovers
Ability: Torrent
EVs: 248 HP / 252 Def / 8 Spe
Bold Nature
IVs: 0 Atk
- Rest
- Sleep Talk
- Scald
- Moonblast
Ability: Tough Claws
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Stone Edge
- Earthquake
- Aqua Tail
- Pursuit
Gengar @ Spooky Plate
Ability: Cursed Body
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Taunt
- Will-O-Wisp
- Hex
- Sludge Wave
Empoleon @ Leftovers
Ability: Torrent
EVs: 248 HP / 76 Def / 184 SpD
Calm Nature
IVs: 0 Atk
- Defog
- Roar
- Toxic
- Scald
Hippowdon @ Rocky Helmet
Ability: Sand Stream
EVs: 248 HP / 84 Def / 176 SpD
Impish Nature
- Stealth Rock
- Slack Off
- Earthquake
- Fire Fang
Hydreigon @ Darkinium Z
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Roost
- Taunt
- Dark Pulse
- Draco Meteor
Primarina @ Leftovers
Ability: Torrent
EVs: 248 HP / 252 Def / 8 Spe
Bold Nature
IVs: 0 Atk
- Rest
- Sleep Talk
- Scald
- Moonblast
That's all, I hope you will like the team