So is Toffee some sort of...royalty? A high-ranking member anyway?>Avarius-Septarsis Treaty
Ludo isn't familiar with Toffee beforehand, so I assume he's not that familiar with his family history.>He was incapable of regenerating after the conflict prior to the Mewman/Monster Accord
So perhaps the way to truly kill him is remove his regenerating ability, somehow.
I can see an episode at least showing either Toffee's origin story or someone going back through his history.