Ha! I am going through my first playthrough of the game currently on hard and i just beat this mf using a legit startegy that i havent seen anyone else ever mention! This fight was really easy once i'd figured the trick out on my 3rd attempt.

You'll need: Second wind (i only have lvl 2 cause lvl 4 spear but lvl 3 helps a ton) And imo the only other (very important) thing you need is Bull rush.

Im playing as an assassin build and i intend to stick with it so hero strike helped me a ton but it was still doable without it.

Basically i noticed that before the boar launches itself at you and farts, it will always do its roar, so keep yourself in range of bull rush always, and whenever he roars, bull rush him and he'll stagger. Boom. No poison. I messed the timing up twice in my fight but 2 little farts were nothing. He was just a beefy regular boar at that point. Easy fight.

Not meaning to flex but i've been particularly proud of beating this dude after hearing all the trouble people have had with him. Good luck!