Nat uses the Fist of Love, it bypasses all defenses!

She clearly has a feat that makes her attacks 1000% more effective when used on allies.

"Graceful Bluff"?

Darkening, you need to add the 5000% extra that bypassed defenses, turn and everything when used against idiots

Bardic inspiration flavored to involve physical correction?

She seems to more of a flavor DnD player then mechanical focused one.

I was referencing that time the crew was shocked that a Marine could floor Luffy with a regular punch; his reasoning is "There's no defense for the Fist of Love!", the Marine is Luffy's grandfather. So sisterly love must be Nami's secret.