Many bad guys lack a certain seriousness, so here is one perfect example how a bad guy should be:
Damien Darkon
Of course, he fits the cliché of a mad/evil/possesed scientist.
But who cares about that when he's aiming with his plasma-railgun-arm on you?
Many evil goodies help him to stay a step ahead of the Rovers.
Will he be ever captured/neutralized/rescued?