Wool-dog

A 'wool-dog' is a girl or guy who possess many negative character traits inherent in toxic people, but superficially seems to be nice.

The term mostly concerns appearance, as visually a wool-dog will look deceptively benign and disarming, but in fact has the personality of a viper.

This contrasts with toxic personalities that visually and behaviorally signal themselves from a distance, or genuinely nice and benign people who look dangerous and/or trouble.

Related to the term "a wolf in sheep's clothing".

Guy 1: "I'm kinda into Cindy, she looks so nice and sweet!"

Guy2: "Nah bro, she's a wool-dog."