I have watched Enterprise and he still came across to me like a "typical mustache stroking villain". I still don't think his turn from good guy to totally bad guy was really plausible.
By the way do we still have to use spoiler tags in this thread? I haven't in previous posts here and I thought that was ok?
Edison felt screwed when the MACO's were disbanded and integrated into the new Federation Starfleet. He then watched his crew die leaving only three survivors...during which he felt abandoned by the Federation. He used/took the life-extending technology on the planet to extend his life...by taking the life force of other people, changing his appearance. He obviously also went insane.