You've dealt with these types countless times before — one of the perks of being able to retain your memories from every past cycle. Once they hit this stage, the only way to get rid of them is to destroy their bodies so thoroughly they become UNRECOGNIZABLE. The most practical way to achieve this is usually through IMMOLATION, which you've had the pleasure of testing a couple times before.
Sadly, you're a bit lacking in flammable resources at the moment. This won't kill him, but you hope he's got a sweet tooth, because when these candies hit they have a tendency to ROT YOUR TEETH OUT.