Mosty, smurf the 10% chance to knock a guy off the battle field. That is a bit extreme. Just go for a 20% Instant death rate. Higher odds of happening, as well as not having a chance of just smurfing you entirely with no real way to overcome. It works quite well since VI only has one relic equip-able by two people which prevents Instant death.

Also, he possesses the ability of the gods of Magic themselves, so I propose the following attack.

Sever Connection - 1 Target
--Effect 1: Removes all Magical buffs, including ReRaise
--Effect 2: Halves the accumulative total of all stats that have been boosted due to Per Level Esper Bonus's.
--Effect 3: Randomly eliminates half of targits Active Spell List.
---Notes: Does not register as a Status Effect, much like Charm in the original version of FF VI. No Duration. Stays on even after revive.