Gen 8 UU
Tentacruel @ Black Sludge
Ability: Liquid Ooze
EVs: 252 HP / 200 Def / 52 Spe / 4 SpA
Timid Nature
- Scald
- Sludge Bomb / Toxic Spikes
- Knock Off
- Rapid Spin
Scald is STAB and has a 30% burn chance, which helps in the defenses department, as even with max HP and 200 Defense EVs, it's not all that good. Sludge Bomb is STAB with a 30% Poison chance to wear things down, Toxic Spikes poisons (or badly poisons) anything other than Steel and Flying types, however it is easier to get rid of, as Defog is common and Poison types aren't too rare either.
Heavy-Duty Boots also completely ignores Toxic Spikes. Knock Off catches switch-ins with its crippling item removal effect, it's not an offensive tool because it doesn't do that much damage, even to Psychic types, because of Tentacruel's low Attack stat and the Timid nature. Rapid Spin removes hazards, which are the main way to wear a bulky Pokemon like Tentacruel down. It also raises Speed which is cool I guess lol