adj. 25B6; adjective
ferocious animals : FIERCE, savage, wild, predatory, aggressive, dangerous.
a ferocious attack : BRUTAL, vicious, violent, bloody, barbaric, savage, sadistic, ruthless, cruel, merciless, heartless, bloodthirsty, murderous; poetic/literary fell; archaic sanguinary.
(informal) a ferocious headache : INTENSE, strong, powerful, fierce, severe, extreme, acute, unbearable; informal hellish.
gentle, mild.