Tentacool Gen5

Tentacool @ Eviolite
Ability: Liquid Ooze
Happiness: 0
EVs: 248 HP / 8 Def / 252 SpD
Calm Nature
IVs: 0 Atk
- Toxic Spikes
- Rapid Spin
- Scald
- Acid Spray / Icy Wind / Knock Off

Last move is customizable. Acid Spray is recommended due to it allowing Tentacool to beat Vigoroth, Natu, and Throh 1v1. This only works if you Acid Spray on the switch however, so the other options are also fine choices for punishes.