Long story short, he was always a slimy asshole, but here are some key points from wikipedia and just in regards to his mayoral position:

• Hated the homeless and tried to have them “removed”(used cops to arrest them and shove them in overcrowded shetlers. A church ended up suing the city for their right to help homeless people)

• “cracked down on crime”, by basically aggressively arresting people for minor crimes like jumping the turnstile.

• Tried to stop multiple community service proogram for the mentally ill, elderly, day-care, etc.

• Big fan of “eminent domain” to take buildings and give them to his sponsors.

• Racist with multiple racist pollcies, many staffers and leaders left because of him.

• He threaten funding for the Brooklyn Musem if they didn’t remove several pieces, specifically including one called “The Holy Virgin Mary” which was of a black person. Calling it a governement-supported attack on christianity and they had to sue the city.

• Campaigned on fixing public schools, but cut $2bill of their budget and $4.7bill from the repairs budget

• Two days after Columbine he said he wanted to “blow up” the Board of Education.

• Wanted to imprison the teachers union president if they went into strike(their contract was up and the city hadn’t started any renegotiation)

• Allegedly cheated on his wife with his spokeswoman

• Tried to threaten Time Warner to have Fox on their cable network, and defended Murdoch when all the surveillance and bribery scandals came about

• His administration lost 22 out of 26 civil liberty lawsuits against them, mostly for trying to stifle first amandment rights.

• He wanted a deal with Virginia in which they had to take NYCs trash, in exchange for them being able to visit NYCs culture sites. He also tried to send it to New Jersey, and announced that wihtout actually talking to them first, at all. This all happened because he closed a landfill 20-30 years too early , because he didn’t like how it looked, so it had to be shipped out of town. Costing millions, causing even more pollution, etc.

https://en.wikipedia.org/wiki/Mayoralty_of_Rudy_Giuliani#Criticisms_and_controversies

And much, much more.