4. Arl Howe (Dragon Age: Origins)
While Loghain's betreyal was about protecting Ferelden, Arl Howe's motivations were mired by his lust for power and freed. He was only looking out for himself. The Human Noble's entire family, except for your brother, was slaughtered. Howe even gloats about it right before you kill him, making it all the more satisfying.
