Kids is a great film but I never had the urge to watch it again.
This thread is going to be full of bad films that are "controversial" due to aesthetics (violence, sex, etc) but I want to focus on a couple that were controversial or ahead of their time.
The Bad Seed
The first American film about a child sociopath. As with Psycho, it shocked and disgusted audiences...but they couldn't look away. Legitimately a good movie.
Suddenly, Last Summer
Amazing film on every level. Delving into why it's controversial would spoil the plot. It's not hard to see why it was blacklisted and why many of the actors and writers of the film didn't talk about it for years.