Excessive force is when more force is used than reasonably necessary. Kara Zor-el (Supergirl) has a whole slew of powers, so has she ever abused them?
Apparently she's been accused of having used excessive force on many occasions, to the point that her "arrests" are now basically being thrown out of court for any criminal with a half-decent lawyer.
Kara: But they're in jail now, where they can't hurt anyone. That's all that matters.
Maggie: As long as they don't use the "Supergirl defense".
Kara: The what!?
Maggie: It's a thing some criminals use to get their charges dropped. It's a perfect storm for a defense attorney. Excessive force, evidence contaminated by debris, vigilante justice...
KARA: "Vigilante justice"?