"Fuck me rigid, Frankie Four Fingers is a right fucking Wrong 'Un. He peeled off Jimmy The Greek's fucking kneecaps with a claw hammer just 'cos he looked at 'is Old Lady funny".
A wrong 'un is a phrase used to describe someone or an action someone has undertaken that you disapprove of. It is not offensive merely an expression. Probably originates from the Midlands in England.
Like its name suggests, the term "wrong-un," (taken from cricket jargon) means "wrong one."
It can be used as a transitive verb, which is means "dry anal sex," since it leads to major complications if you try to say "dry wrong-unal sex."
As a noun, the term "wrong-un" is one's arsehole, and the term "dry" doesn't come into play.
As a transitive verb: "Hey, Scotty! I heard ya gave ya woman dry wrong-un!"
As a noun: "Hey, I heard you got some on the week-end, Scotty. Do you do her up the wrong-un? Ha, ha, ha, ha, ha!"