How Do You Even Kill The Boss Thing In Thanos Vaults?

Im an assassin currently, it is impossible to kill this big thing, u can't see it's hitbox, nor how much health it has left.. Ill pay someone to help me kill it ffs.

 

To be honest, for this boss, just be patient
It might take some time to kill, but soon you will be able to wreck it

 

It doesn't matter if you see how many health it has left. Just keep on hitting it.
However, the Giant may be able to one-shot you, so I suggest you go into this shelter:

(in-between the fence and the wall)
He won't be able to touch you, however the minions will, but they aren't the ones who can one-shot you.
Once you are in there, or any other shelter you would like to use, just attack him from there, and he will eventuall die.

 

When fighting a giant using assassin class , I tend to spam Smoke Bomb as it is a medium range AOE and I can just wait them to go into the smoke.