[REQUEST] Can you competitive geniuses out there help me?

[P35]

Hey guys! Can you give me advice on my defensive toxapex?
im not sure if I should run regenerator or merciless. I'm also not sure on the moveset.
Here's what I have so far:
Bold 
Evs- 252 hp 252 def(maybe sdef) 4 speed
recover
toxic 
haze
???
almost perfect ivs 

Any advice for the fourth move or just in general? Thanks in advance 

[Tenebris]

I'm assuming this is for singles, but you should have an attacking move like Scald in your fourth slot so you don't get taunted by opposing pokemon into a struggle.

For the item, Black Sludge is imo the best item for him, at least in battle spot where you can only have one kind of item per pokemon, you can have black sludge on toxapex and leftovers on another pokemon, plus it's a nice item to recover hp with his built-in tankiness.

Regenerator is the preferred ability since toxapex isn't an attacker, which means he can't make the best use of merciless.

All the other things look good, best of luck to ya

[croissant]

your ev spread is fine, but i'd recommend 252 hp / 196 def / 60 def if it is for single battles, run scald for the last move and the ability should be regenerator. yoi can consider toxic spikes > toxic too. black sludge or rocky helmet are good items for it, tho black sludge is generally better.

[P35]

I'll keep both of your suggestions in mind. Thanks!