If your Great Aunt Maude tells you you've become a dissipated bum, she means you don't think of anything but how much fun you're having. If you got a summer job and stopped playing arcade games all day, she might change her tune.
The adjective dissipated is used to describe people who've lost their moral center, and instead of following the rules of conventional morals, prefer to be utterly self-indulgent. The word comes from the verb dissipate, which means "to disperse," but as an adjective it's always used for people who've gone wrong in some way. If you really want to lay into someone, use these synonyms and call him a "dissipated, dissolute, debauched, degenerate jerk."