He did A LOT, it would be best to just read about him.
https://en.wikipedia.org/wiki/Mayoralty_of_Michael_Bloomberg
I would consider him a centrist, rather than being a part of either of the two main parties. This city is where it is now in terms of real estate development and desirability in large part because of him, as he was in bed with the real estate industry and VERY pro development. But as a result, this caused our biggest current issue, an increasingly bad homelessness problem and real estate prices being untouchable for the average person.
Plain and simple, he gets shit done one way or another. I think people greatly underestimate him because he entered the race late. Yes he's going to get hammered on the "stop and frisk" issue at the debate, but I would in no way be surprised if he continues to take the majority of support from other mainstream democrat candidates, but he won't be swaying the more progressive wing at all. I still see him making this a tight race to the end.