Alternatively, throw an elixir or cast Life on him to kill him instantly.
Vivi’s bio should be able to inflict 1100-2000 at that time, and all of your character should have body temp by now. Eiko should have already mastered phoenix if you need to revive someone. If you want to steal some items just be sensible and have the anti-bad status abilities equiped on.
This goes for everyone who is playing this game. let your characters learn every ability they can!