青面獠牙

qīngmiànliáoyá
ferocious-looking (idiom)

CEDICT

green-faced and long-toothed; terrifying in appearance

Wiktionary

脸色青绿，长牙外露。形容面貌非常凶恶可怕。《西游记．第十一回》：「幸有崔判官唤一青面獠牙鬼使，喝退了建成、元吉，太宗方得脱身而去。」《红楼梦．第八十一回》：「疼的眼睛前头漆黑，看见满屋子裡都是些青面獠牙拿刀举棒的恶鬼。」也作「青脸獠牙」。

重編國語辭典

面容非常凶恶可怕

維基詞典

Entry Composition

1 青 qīng
  1. green
  2. blue
  3. black
  4. youth
  5. young (of people)
=2 面 miàn
  1. face
  2. side
  3. surface
  4. aspect
  5. top
  6. classifier for objects with flat surfaces such as drums, mirrors, flags etc
=2 面 miàn variant of 面 miàn
=2 面 miàn
  1. flour
  2. noodles
  3. (of food) soft (not crunchy)
  4. (slang) (of a person) ineffectual
  5. spineless
3 獠牙 liáoyá tusk; fang