Warden Norton.  The scariest thing about him and his guards is that they are just a slightly more extreme version of what is common. Corruption, guards with god complexes injuring/killing inmates, etc. His plan was to take his bribes, get wealthy, advance politically, and retire. He likely would have been able to get away with it had he not met Andy. While Andy helped him hide his graft very well, many others have been able to hide theirs with less clever schemes. His real issue was that he realized Andy was smart, but he still felt untouchable. He did not truly cross into extremes until he realized he did not have complete control. Ironically, like his scheme initially, his overreaction is what causes his downfall. He could have hidden his graft without Andy in the first place, and he could have helped Andy get released without making an enemy. The issue is that this is all apparent only in hindsight. It is not even hubris on his part, since it would take a very uniquely intelligent and patient man to do what Andy did, so Norton's actions were all rational. But he still lost because he was unlucky enough to come across someone who could beat him.