The incarnation of an individual as might in appear in some alternate douchebag reality.
Sitting across from him in the cafe, Tom spied a man nearly identical in terms of dress and appearance, save for a telling look of undeservedly smug satisfaction. Tom had met his douchelganger.
The douchebag version of yourself; someone who resembles you, but is a douchebag. (From the slang "DOUCHEbag" + the German "doppelGANGER" meaning someone who resembles someone else.)
Tyrone is a great guy; Robbie looks like Tyrone, but Robbie is a douchebag. Robbie is Tyrone's douchelganger.