offender, wrongdoer - a person who transgresses moral or civil law

ambusher - an attacker who waits in a concealed position to launch a surprise attack

avenger, retaliator - someone who takes vengeance

brute, savage, wildcat, beast, wolf - a cruelly rapacious person

bludgeoner - an assailant who uses a bludgeon

bully, hooligan, roughneck, rowdy, ruffian, yob, yobbo, yobo, tough - a cruel and brutal fellow

harrier, harasser - a persistent attacker; "the harassers were not members of the regular army"

marauder, piranha, predator, vulture - someone who attacks in search of booty

night rider, nightrider - member of a secret mounted band in United States south after the Civil War; committed acts of intimidation and revenge

raper, rapist - someone who forces another to have sexual intercourse

shedder, spiller - an attacker who sheds or spills blood; "a great hunter and spiller of blood"

slasher - someone who slashes another person

stabber - someone who stabs another person

lapidator, stoner - an attacker who pelts the victim with stones (especially with intent to kill)

initiator, instigator - a person who initiates a course of action