to act as accomplice to the tiger / to help a villain do evil (idiom)
狐狸尾巴
hú li wěi ba
lit. fox's tail (idiom) / visible sign of evil intentions / to reveal one's evil nature / evidence that reveals the villain
曹操
Cáo Cāo
Cao Cao (155-220), famous statesman and general at the end of Han, noted poet and calligrapher, later warlord, founder and first king of Cao Wei 曹魏, father of Emperor Cao Pi 曹丕 / the main villain of novel the Romance of Three Kingdoms 三國演義|三国演义
恰吉
Qià jí
Chucky, murderous villain of the 1988 US horror movie "Child's Play"