And so, the time has come. The time has come to end this fight and the Second War of the Magi once and for all. You ready? Because you don’t have a choice!
Kefka… He can use a basic attack, Havoc Wing (quadruple-power Attack), Firaga, Blizzaga, Thundaga, Meteor, Ultima, Trine, Forsaken (party-wide magic attack), Vengence (party-wide Dispel for positive statuses), Heartless Angel (infamous move in Kingdom Hearts and other Final Fantasies; reduces HP to 1 for all party members), and Hyperdrive (a super-powered, unblockable, barrier-piercing attack; you’ll probably get killed by it).
Hell awaits… Kefka begins with Heartless Angel; if you have any Megalixirs, use it RIGHT THEN. Otherwise, Curaga and move on. You’re lucky on offense; Kefka won’t absorb anything or change his elemental data. Not much to be happy about, though. Since you SHOULD have used a damn Megalixir, you’ll be okay-ish for a little bit. You’ll be able to put Reraise on. That’s a priority.
Anyways, offense… Bahamut, Quick -> Ultima, Flare, Meteor, other non-healing Espers… Celes should be the one exception, sticking on Runic duty constantly to fend off the brunt of the attacks.
Granted, I did just generalize the strategy. But it IS kinda hard to do more than that. Maintain your offense, heal when needed, and good luck.
After the battle, you’ll watch a nice, lengthy ending. Take the time to blink so you can read this: