Could someone give me some advice on? The battle's really easy until the final phase. Then he uses that ability that gives my whole party every status effect and starts spamming Almighty spells. The Almighty wouldn't be that big of a deal if I could heal, but everyone's incapacitated by his super status ailments. Mamudoon is also annoying, but again not a big deal if my demons could actually act.King Kenji
Get a null ailment skill, preferably on the majority of your party (and a null accessory for the MC). If any of Ancient Curse's ailments are nullified the attack has no effect. Kenji should only be spamming megidolaon if all of his other attacks are absorbed or nullified. Swap out the offenders with demons who resist the elements instead of nullifying them.