The main streams and funny memes aren't dark, user created streams can be a bit darker, and I wanted to say it's also odd how who_am_I got so many points. IP has a lot of drama so it's after that, and lewis0428 is a racist moron. The meme wars need no explanation, and MSMG is just dark and horrible.
Raydog dissapeared oddly 8 months ago, he was one of imgflip's most famous users for years on end.
Randomname27 committed suicide. The ppolice is a stream dedicated to stopping porn in imgflip by reporting it to the site mods, but recently they got threatened to be banned for "harrasment" despite helping the mods for months. Hackers are sometimes a problem, but not usually. Still pretty dark.
And for the last one, you can find r34 templates if you look for long enough. Nobody knows who they were made by as you can't tell who made something just by looking at the template's description, so they can't be banned either. It's why I stopped looking through templates.