Go with touch attacks, they disregards armor ;)
They will ignore armor, natural armor, shields, and othershields. Other bonuses still apply.
So have a pro wrestler attack the OP PC (grapple).
You could also throw acid flasks or alchemist fire (again touch attack, ranged this time). There is also a net that can be thrown.
Or simply be generous with the finding of magic items, and scale the villains up a bit. This class is clearly OP in a world with few magic items, but what the PCs find is your call.
A large monk with high STR can be very effective against him. When my player minmax, I tend to do the same. Don't worry about finding reasons for why a monk should be hunting him, he will give you plenty by destroying relics ;)
Also, don't forget that to be resurrected, the target must be willing :) I doubt a forsaken would accept magical help, so don't be too hard on him (unless he has only taken this class for the bonuses, and not the RP).