The way Mandark just sits there for his death is so...distraughting. I can really see all the pain he's gone through. Although I can't believe this is just another "Oh, shouldn't we help the bad-but-pity guy? We don't have any time, let's just leave him here to die!" excuse. -_-
Interestingly, according to Mandark's article in the FusionFall Wiki, it says "Mandark's love of Dee Dee also caused him to be manipulated by her evil doppelganger, Fusion Dee Dee, making him steal Dexter's wrench."