perpetrator, blame, fault, malfeasor, scapegoat, guilt, trouble, wrongdoer, misfeasor, culpa, more...

victim, innocent

villain, perpetrator, offender, murderer, aggressor, abuser, more...

real, main, chief, major, likely, true, only, primary, principal, common, prime

guilty person,   person at fault,   one to blame,   the one responsible,   the suspects,   the guilty,   one guilty,   guilty one,   the one to blame,   a guilty person