It was clear from the start that Frank had no qualms about building up Peter Russo only to destroy him in order to further his own means. However, it appeared as if he had at least some remorse about what he was doing, and there were times that it seemed like he may have even cared about Peter. Everything Frank did was for himself though, and when the troubled Congressman became a problem, things took a shockingly sinister turn. Whatever despicable or manipulative acts the viewer had seen Frank commit over the course of the first season, they all paled in comparison to him murdering Russo by staging his suicide. The fact that it wasn't planned makes it worse in some ways, as it showed that he was willing to do anything and everything at any time to achieve his goals, even if that was ending a life. Sure, it felt like a mercy killing in some ways, but that's hardly the point!
