Green’s Dictionary of Slang

buttfucker n.

also butt-banger
[buttfuck v. (1)]

one who indulges in anal intercourse.

[US] in B. Jackson In the Life (1972) 324: Everyone was ‘Old Butt-Fucker’ to him.
[US]‘Victoria Parker’ Pay for Play Cheerleaders [Internet] Travis blew his load in Chrissie’s asshole. [...] ‘You bad little butt-fucker!’ Chrissie huffed, her body shuddering.
S. Hunter Dirty White Boys 1: Lamar wasnt’ a fag, although, when the spirit moved him, he was a buttucker.
[US]F.X. Toole Rope Burns 195: You ever thought of being a fighter instead of a butt fucker?
[US]J. Ellroy ‘Hollywood Fuck Pad’ in Destination: Morgue! (2004) 214: Fruit Alert: butt bangers in backseat bliss.