Damon's certainly had an uneven path to roam, but his checkered past is not as deadly as viewers may have believed when we met bad boy Salvatore. His arrival in Mystic Falls in 2009 heralded a number of deaths including Vicki Donovan and Coach Tanner. While Damon didn't kill Vicki once and for all, he did attack her twice and turned her (because he was bored). Later he disposed of the body after brother Stefan staked her to keep her from ripping Elena's throat out.
But it turns out, that Damon has a reason to be pissed at his baby brother. We found out during the first season that Stefan forced Damon to turn. As time trickled on, we found out that after turning, Stefan was a ripper—an out of control monster when he killed and he liked keeping the bodies around. Damon couldn't help him, so he left him to Lexi.
Flash forward to 2011, Damon took a lot of knocks including the discovery that love of his life Katherine was a lying, manipulative bitch. When she came after Elena, Damon and Stefan worked together at the end of 2010 to toss her happy ass into the tomb, imprisoning her as Damon had mourned for over a century. Now the brothers must struggle with the fact that they are in love with the same woman...again.