firm (adjective) firm: inflexible
Sinonime: assassin, butcher, criminal, cutthroat, enforcer, executioner, hit person, hit-and-run, homicide, killer, manslaughterer, manslayer, massacrer, perpetrator, slaughterer, slayer, soldier, trigger person, triggerman
Antonime: flexible,
loose,
slack,
soft,
supple,
weak,
yielding