Counter that Pokémon!

Celebi @ Psychium Z
Ability: Natural Cure
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Nasty Plot
- Psychic
- Giga Drain
- Dazzling Gleam

Bronzong @ Leftovers
Ability: Levitate
EVs: 252 HP / 4 Def / 252 SpD
Sassy Nature
- Stealth Rock
- Toxic
- Gyro Ball
- Psywave

Even at +6 Shattered Psyche only 2HKOs. Bronzong can tank your hits and kill you off with Toxic + Psywave.

Heatran @ Steelium Z
Ability: Flash Fire
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
- Magma Storm
- Earth Power
- Flash Cannon
- Stealth Rock

Mantine @ Leftovers
Ability: Water Absorb
EVs: 252 HP / 36 Def / 220 SpD
Calm Nature
- Roost
- Scald
- Air Slash
- Toxic