Kiwi farms is extremely racist and hateful but in terms of damage i think there are tons of reddit, discord, Facebook communities that are just as bad. Reddit allows communities that do everything they can to interfere and destroy people. I'm pretty sure reddit bullied some animal sanctuary youtber to suicide a few months ago.
Extreme anti social behaviour is so mainstream now it blows my mind. When I see it on the fringe of the internet I'm not surprised but when its right there on the most popular websites with hundreds of thousands joining in it makes me sick. The only difference between these communities and KF is that KF users can say slurs and dont have to mask up their language.