I'm not the best at making OP kits

An awesome idea for an episode IX legendary would be a mythical Supreme Leader Kylo.

Requiring Jedi Rey (released prior) and 4 Resistance characters (17,500 power minimum)
As well as, Supreme Leader Snoke (legendary or marquee?) As well as 4 other first order characters (17,500 power minimim)

Supreme Leadee Kylo would basically be a meta defying version of KRU but synergies best with KRU, Kylo Ren and other FO allies. Changing the meta from Jedi Rey (speculation) to First Order. His kit being,

(Basic) Furious Slash: Deal physical damage to target enemy and recover 10% max health. If the enemy was buffed, dispel all buffs. If the enemy was debuffed, stun them for 1 turn.

(Special) Savage Strike (Cooldown 4): Deal Physical damage to target enemy. Recovering health based on 25% of the damage dealt. If Kylo has no protection, this attack deals double damage. Reduce ability cooldown by 3 on a critical hit.

(Special): STOP! (Cooldown 5): Kylo deals special damage to all enemies and stuns target enemy for 2 turns. If kylo was debuffed, kylo dispels all debuffs on himself and every first order ally. Each unit recovers 2% protection and 2% max health per debuff dispelled on them.

(Leader) Supreme Leader Of The First Order: All First Order allies gain +35 speed, 25% crit chance, 50% crit damage and recovers 5% protection and 5% max health for each critical hit. Every time a first order character takes a turn they gain advantage for 2 turns.

(Unique) Useless Servants: Whenever a first order ally is defeated, Kylo reduces his cooldowns, takes a bonus turn and gains 50% offense and 25% defense (stacking) until the end of the encounter.

(Unique) Furious Rage: Whenever Kylo gets reduced to 50% health or lower, Kylo becomes enraged, takes a bonus turn and gains the following, 100% offense, 100% defense, 50% speed and 100% tenacity (undispellable) for the rest of the encounter.

This is because of Kylos "Anger Issues"