attenuate, debilitate, enervate, enfeeble, sap, tire, undercut, undermine, weaken

hobble, lame

maim, mutilate

knock out

dismember, hamstring, hobble, paralyze

batter, bruise, bung up, mangle, maul, rough (up)

gore, lacerate, wing, wound

disfigure, scar

kneecap

break, damage, harm, hurt, impair, injure

bash, beat, belt, bludgeon, buffet, drub, hammer, lace, lambaste (or lambast), lick, paste, pelt, pommel, pound, pummel, thump

bang, box, hit, punch, slap, smack, smash, sock, spank, swat, swipe, thrash, thwack, whack

flog, lash, wallop, whip

kill, murder

torment, torture