you could also just keep KotR and just reduce the multiplier it uses, like possibly lowering the damage per hit from 137800 total damage (10600 a hit) at max stats to 41340 damage (3180 a hit) by making the multiplier reduced from 80 to 24. max stats bahamut zero does 15900 damage, and costs 70 less mp to use, so this would be a much nicer amount for KotR to do, though it could still probably be reduced to a mod of 16 instead, doing 27560 damage (2120 a hit), which balances out pretty nicely with the other summons' strength to cost ratio (though ~14 for the mod would be even closer).
they just made it way too powerful, making it do as much as casting neo bahamut 16 times in one attack, rather than making it have around the omnislash multiplier, which is where it needs to be at for sane damage for it's cost. bahamut zero gets about 88 damage per mp at max stats, while KotR gets 550 per mp cost, definitely way too high. it should be around the 100 mark, since the lower summons have slowly increased to this amount, and ~100 per mp would be the last step, and is about where a mod of 14 to 16 sits around, 14 being my opinion of the best amount.
you can change the attack to supernova if you want and can, but i think that you should just make KotR have a mod of 14 or so if all you are removing it for is because of the damage output. with a mod 14 KotR, you could actually quadra magic comet to do more damage than it would (it could use weakening as well XD), since it does 151 per mp, and at four uses, that would cost 280 mp, only slightly higher than KotR, against one enemy that is, against a group KotR is still better
. there is a lot of balancing the moves need done, and i think changing them because of power should be last resort stuff, while removing, say chocobuckle, a move that would take hours to pump up to decent amounts, for a custom move that saps life/mp from the enemy or something (anything would be better in my opinion <_<). but i guess it is all up to opinion, so if you can change KotR to supernova, then give sephy a taste of his own medicine
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