Harry Potter and the Deathly Hallows
Affiliation: Order of the Phoenix
Mundungus is a coward, and in Deathly Hallows he totally lives up to his nickname, Dung (we can't blame the guy, with that nickname). He's always been a somewhat reluctant member of the Order of the Phoenix, and is mostly concerned with saving his own skin. In Chapters 4 and 5, Mundungus is one of the decoy Harry Potters, and is paired with Mad-Eye Moody. Terrified of the Death Eaters pursuing them, he deserts his post, leaving Mad-Eye to get hit by a Death Eater's killing curse. It's one of the least courageous moves we see throughout the entire book and many battles.