actually, merciless toxapex is more of a beast. sure regenerator is a good ability, but with merciless, you can use baneful bunker (toxapex's special move) and either poison the target or just protect yourself. and if the target does get poisoned, head in there with poison jab or venoshock and get a bunch of critical hits. this it the toxapex i use (moveset and item only)
Toxapex/Nickname: Ashley/ Item: poison Barb/ Ability: Merciless
Moveset
Recover
Baneful Bunker
Poison Jab
Scald (im thinking or replacing that with either Liquidation or Waterfall)
So yeah try Merciless toxapex