rotter
noun.
a person who is deemed to be despicable or contemptible
only a rotter would do that|kill the rat|throw the bum out|you cowardly little pukes!|the British call a contemptible person a `git'
Synonym: bum, stinker, so-and-so, skunk, scum bag, rat, puke, lowlife, git, dirty dog, crumb, stinkpot