Green’s Dictionary of Slang

1. outstanding.

1989

P. Munro Sl. U.

2. strong, powerful, aggressive.

1989		P. Munro Sl. U. 52: That bar has a butt-kicking security guard.
1993		T. Jones Pugilist at Rest 215: He was tough. He was a butt-kickin’ stud.
2000		Guardian Rev 21 Apr. 16: It is head-clearing, butt kicking and high on its own sophomoric humour.