Mega Gyarados

252+ Atk Scarf/Icium Kyurem-B: 0+ or 68 Atk, 72 HP / 252 Def or 252 HP / 96 Def
252+ SpA Scarf Porygon-Z: 164 SpD or 252 HP / 80 SpD
Mega Charizard Y: Stone Edge
Speedy Taunt+Iron Defense Deoxys-D: Taunt, Crunch, 128+ Atk
Mega Pinsir: Stone Edge, 116 Spe
Non-Air Balloon Magnezone: Earthquake, 172 Spe
Bulky Fairium Mimikyu: Iron Head
Genesect: Fire Blast, 100 SpA
Greninja: 128 Atk / 128+ Spe or 0+ Atk / 216 Spe
Mega Heracross: Bounce | 64+ Atk / 128 Def or 240 HP / 64+ Atk or 64+ Atk / 208 Spe or 240 HP / 208 Spe or 128 Def / 208 Spe
Kartana: Flamethrower or Fire Blast
Meloetta: Crunch | 244+ Atk / 92 Spe or 244+ Atk / 164 SpD or 188 HP / 244 + Atk or 164 SpD / 92 Spe or 188 HP / 92 Spe
Charm Chansey: Substitute
Ferrothorn: Fire Blast, 100 SpA [More SpA necessary if investing into HP]
Buzzwole: Bounce
Durant: Flamethrower or Fire Blast
Avalugg: Fire Blast, 8- SpA
Relicanth: Substitute
Pyukumuku: Substitute
Mega Scizor: Flamethrower or Fire Blast