Devious
Cunning, Crafty, Wily
い adjective
Someone who is bad but also clever (賢い) is someone who is using their cleverness for evil. When you refer to clever evil people, usually you describe them not as "clever" but as devious, cunning, or other things.
わるがしこい
The reading is 悪い and 賢い combined together into one word. Be careful of the rendaku.
あいつは悪賢い男で、猫かぶりが大のお得意なんだ。
He’s such a cunning guy and he’s very good at feigning innocence too.