Bro how do you kill a pseudo giant

So I am at bloodsucker village and I see the side quest to kill the pseudo giant my first time encountering a pseudo giant.

Now I need to kill this thing so the guy will show me his stash for the grom s-14 now I know there is a grom s-14 across the river but I need two to do the ammo glitch (because u could not find any ammo) but I had 24 deaths on my current play through before but now I have 38

But someone please help where are the weak spots.