禍首

祸首
huòshǒu
  1. chief offender
  2. main culprit

CEDICT

Entry Composition

1 禍 huò
  1. disaster
  2. misfortune
  3. calamity
2 首 shǒu
  1. head
  2. chief
  3. first (occasion, thing etc)
  4. classifier for poems, songs etc