AV amoonguss takes on greninja, koko, kartana, bulu, keldeo, and has enough physical bulk to take some hits from landorus and lopunny. Basically it does venusaur things while having regenerator to not get worn down as quickly as venusaur. I would suggest this set
Amoonguss @ Assault Vest
Ability: Regenerator
EVs: 248 HP / 252 Def / 8 SpD
Relaxed Nature
IVs: 30 Atk
- Hidden Power [Fire]
- Giga Drain
- Clear Smog / Sludge Bomb
- Stomping Tantrum
HP FIRE IS A NECESSITY so you beat kartana which is amoonguss's main drawing point as a bulky grass. Max defense with an av seems counterintuitive but the physdef is needed to take on kart while the av makes it bulky enough for specs gren and koko. Leftovers/Rocky Helmet can be used over av and makes moveslots for status moves, namely stun spore and spore. Foul Play and HP Ice are pretty bad options on amoonguss.
I guess you could forgo hp fire and run eject button amoonguss into scarf zone new meta gang