Anakin fell to the dark side for all the "Right" reasons if there ever was any. Though there are never right reasons for evil, his was the most pure. Only later did he become corrupt, and jealous.
I admit Malak was the master of his own fate, but he was Revan's most loyal ally and probably also felt honour bound. And to be fair, neither Malak, nor Revan willing fell. They were controlled by the emperor, but alas later they broke free, and still kept upon their path. So...yeah they both willingly did it, so this whole ramble was pointless...awkward
