[Corinthian]

The big question is what kind of resistances it have. If it is not cold immune then Numbness/frozen heart will fatigue it out at witch point protection and HP probably wont mater much. If it is not shock immune then lightning spells can do the same. Fire spells are a bit worse when it comes to causing fatigue, but creatures with heat auras like devils and dust warriors will work fine. Regrettably, poison probably wont work well because of the regen.

If you dont have any other option then (large numbers of) elite troops with strength of giants and weapons of sharpness will kill super combatants just fine. If they have magic weapons then that would be a bonus.

PS: Knai, the Hell sword is kind of useless because unlike the spell, the sword allows for an MR save.