Employing Ghislaine Maxwell has to top the list. Changing their community rules definition of hate speech to only be against chosen groups has to count too. But there’s a lot of bad stuff that redditors quietly accepted, forgot, or newer members never heard of.
I also seem to recall one of the gun subreddits, I don’t remember if it was guns or firearms or weekendgunnit, asking express permission to etch the reddit logo and subreddit name into a gun. They received permission, posted pictures, and later received a cease and desist.