a person or thing that is universally detested or scorned by everyone

To feign sympathy or sorrow for someone one has harmed; hypocritical pretense of condolence.

literally, a dog that catches mice

it doesn't matter whether a cat is white or black; as long as it catches mice it's a good cat (Deng Xiaoping's famous saying favoring pragmatism over ideological purity)

a single negative person or element that ruins an entire group or situation

(finance) a form of front-running in which a fund manager secretly builds a position in a security at low prices using personal funds, then uses public funds to drive up the price

lit. rat's tail; fig. a follower of inferior stature

like mice trying to pull a turtle, having no way to grip it; used to describe being unable to find a starting point for a difficult or unfamiliar task

indicates that the most significant, difficult, or substantial part of a situation is yet to follow; the worst is yet to come

mouse hole

describing a person or thing that is hated by everyone and pursued by all; a social pariah

the 'at' symbol (@) used in email addresses and social media

one small negative element or person that ruins an entire group or situation