yīn​xiǎn

insidious

阴险 (陰險) yīn​xiǎn
insidious adjective
treacherous, sinister, or crafty; having hidden malice in one's character or actions

That person is insidious and ruthless, always plotting against others behind their backs.

Frequency

Movie subtitles
3.28 per million appears in 2% of films
Written text
2.35 per million

Sources

Definitions
CC-CEDICT