No, no he doesn't. Maybe you've been watching a different show but:
1. The guys at the bar literally drew a gun on him and he fired to defend himself at the last second. That's not murder, it's self-defense.
2. Again, the prisoners tried to kill him, that's not unnecessary although I'll give you that the one he left to the walkers was pushing it and this was Rick's one and only break. You'll remember that he spared two of them. Shane would have killed them.
3. Rick was trying to give Shane every opportunity, which is why he followed him into the woods.. hoping Shane would change his mind.
4. Shane could have given Otis the respirator and sacrificed himself, which would have been the right thing to do. (Even though we've been over this, those zombies were a mile away and neither was in any real danger.)
5. Shane Killed that kid to lure Rick out, again, evil intent.
Not only what you do, but why you did it is the final deciding factor of if it's a villainous act or not.
I think you are confused. I never said that Rick was the hero, just that Shane was decidedly the villain. Although that Laurie argument could certainly be made. You are also confusing threat level with the validity of their villain status, Dick Dastardly is probably the most ineffective villain ever, but he's still a villain.