I dont see mike as a tragic character i see him as a person who just made bad choices and had to live with them. Mike had the best oppurtunity to finish college and live a straight life but he chose not to. Sure he claims it was to protect his family but mike wanted to be wealthy and powerful. I mean if he really wanted to be legit mike could have let others be the don and just lived a straight lifesyle but deep down he was greedy as anybody. also mike state of mind deteriorated once he killed people in cold blood. Some people feel regret and someone people become more cold blooded which is what happened to mike