Ferocious; brutal — describing someone or something that is violent, aggressive, and dangerous (commonly used as a na-adjective, e.g. 凶暴な犬).
凶暴な犬に近づくと危ないから、柵の外にいてください。
It's dangerous to approach a ferocious dog, so please stay outside the fence.
事故後、その動物は驚いて凶暴になってしまった。
After the accident, the animal was frightened and became aggressive.
彼は普段は温和だが、怒ると凶暴さを見せることがある。
He is usually gentle, but when angry he can show a violent side.