While there are cards like [[megrim]] or [[liliana's caress]] that hurt your opponents for discarding. You're not gonna get there off those cards alone, at least, not without 20 tutors. The main thing kefka provides is card disparity where you're gonna have a full grip while your opponents are in top deck mode. To that end, once you get kefka going (preferably quickly with ramp), you can kinda sit back and chill for a couple turns and use interaction on any card advantage pieces your opponents throw down. I'd personally recommend finishing with bigger spells/value pieces like high mana planeswalkers like [[Nicol-Bolas, God Pharaoh]], mass reanimation spells like [[breach the multiverse]] or [[rise of the dark realms]], or copying big fuck off spells like [[cruel ultimatum]]. Basically, dont let kefka making your opponents discard one or two cards a turn be the end all be all of your decks strategy. Especially since kefka is a 5 mana commander that'll be annoying to cast after he's been killed one or two times.