[Snake]

I mean, it does have a relatively long cooldown but it doesn't do anything special, so why not?

Currently what kills me is the 'why bother ranking checkmate up' when you can just spend one point for the same effects of it at rank five, for just a small FP eating? That suggestion of giving it one way to avoid something that would impair this decisive attack sounds genial to me.

Also, people with 15% HP are already one feet to the grave, checkmate is just a kind welcome for them to stay down. But maybe, just maybe, it shouldn't ignore Last Chance if it's incapacitating enemies a la Grandupper.

Also, another condition for the Rank 5 to happen could be 'only if you are wearing Heavy Armor'? And then chance the base effect to 'doubles the Scaled DEF bonus damage'.

Rank 5: 25 FP, Doubles the bonus Scaled DEF damage. If you are using Heavy Armor, and the enemy has less than 15% of their maximum HP, they will be instantly incapacitated.