I want to share another set I had great success with:
Gyarados-Mega @ Choice Band
Ability: Tough Claws
EVs: 252 HP / 252 Atk / 252 Def / 252 SpD / 252 Spe
Adamant Nature
- Pursuit
- Knock Off
- U-turn
- Ice Hammer
With the combined power of 155 base attack, choice band and tough claws, it really hits like a truck. Some calcs:
252+ Atk Choice Band Tough Claws Gyarados-Mega Knock Off (97.5 BP) vs. 252 HP / 252 Def Registeel: 229-271 (62.9 - 74.4%) -- guaranteed 2HKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Pursuit vs. 252 HP / 252 Def Aegislash-Shield: 378-446 (116.6 - 137.6%) -- guaranteed OHKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Knock Off (97.5 BP) vs. 252 HP / 252+ Def Giratina: 492-582 (97.6 - 115.4%) -- 87.5% chance to OHKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Pursuit vs. 252 HP / 252+ Def Giratina: 408-480 (80.9 - 95.2%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Choice Band Tough Claws Gyarados-Mega Ice Hammer vs. 252 HP / 252+ Def Fur Coat Zygarde-Complete: 336-396 (52.8 - 62.2%) -- guaranteed 2HKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Pursuit vs. 252 HP / 252+ Def Kyogre-Primal: 246-291 (60.8 - 72%) -- guaranteed 2HKO
Pursuit allows it to kill mons that want to switch out, like Giratina, Aegislash, MMY that is choice-locked into Psystrike, and poison healers that got their ability suppressed but didn't switch out immediately.
Knock Off hits insanely hard, provides utility in removing items and is the main attacking move, while Ice Hammer nails Yveltal and Zygod who want to absorb a Knock Off and U-turn provides momentum and allows to bluff a RegenVest set early in the battle.
Gyarados-Mega @ Choice Band
Ability: Tough Claws
EVs: 252 HP / 252 Atk / 252 Def / 252 SpD / 252 Spe
Adamant Nature
- Pursuit
- Knock Off
- U-turn
- Ice Hammer
With the combined power of 155 base attack, choice band and tough claws, it really hits like a truck. Some calcs:
252+ Atk Choice Band Tough Claws Gyarados-Mega Knock Off (97.5 BP) vs. 252 HP / 252 Def Registeel: 229-271 (62.9 - 74.4%) -- guaranteed 2HKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Pursuit vs. 252 HP / 252 Def Aegislash-Shield: 378-446 (116.6 - 137.6%) -- guaranteed OHKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Knock Off (97.5 BP) vs. 252 HP / 252+ Def Giratina: 492-582 (97.6 - 115.4%) -- 87.5% chance to OHKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Pursuit vs. 252 HP / 252+ Def Giratina: 408-480 (80.9 - 95.2%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Choice Band Tough Claws Gyarados-Mega Ice Hammer vs. 252 HP / 252+ Def Fur Coat Zygarde-Complete: 336-396 (52.8 - 62.2%) -- guaranteed 2HKO
252+ Atk Choice Band Tough Claws Gyarados-Mega Pursuit vs. 252 HP / 252+ Def Kyogre-Primal: 246-291 (60.8 - 72%) -- guaranteed 2HKO
Pursuit allows it to kill mons that want to switch out, like Giratina, Aegislash, MMY that is choice-locked into Psystrike, and poison healers that got their ability suppressed but didn't switch out immediately.
Knock Off hits insanely hard, provides utility in removing items and is the main attacking move, while Ice Hammer nails Yveltal and Zygod who want to absorb a Knock Off and U-turn provides momentum and allows to bluff a RegenVest set early in the battle.