Fierce
Part of speech: adjective
Definition: Extremely violent, severe, ferocious or savage. Resolute or strenuously active. Threatening in appearance or demeanor. Irish rural slang for "very" or "excellent." Of exceptional quality, exhibiting boldness or chutzpah.
Example sentence: I do not believe in using women in combat, because females are too fierce.
Merciless
Part of speech: adjective
Definition: showing no mercy; cruel and pitiless
Example sentence: Thought is subversive and revolutionary, destructive and terrible, Thought is merciless to privilege, established institutions, and comfortable habit. Thought is great and swift and free.