bad egg

Translations
нехороший человек
Despite his charm, he's quite the bad egg in the group.
Несмотря на его обаяние, он довольно-таки нехороший человек в группе.
Definitions
A 'bad egg' is an informal term used to describe a person who behaves dishonestly, unethically, or causes trouble; essentially, someone who is considered to have a bad character.
Words
bad

adjective
плохой
egg

noun
яйцо