also: ハッたおす
godan verb (-su), transitive verb
Rough, colloquial verb meaning to hit someone so hard they fall down. Stronger and more violent than 倒す alone. Often used in fights or threats.
See also: 張り倒す (はりたおす)
あいつを一発ではっ倒してやる。
I'll knock that guy down with one punch.
彼は相手を張っ倒して勝った。
He decked his opponent and won.