DDoS is still not that serious, unless it's against the server.
Doxing is fucking terrible. I'm completely okay if it's just me that's affected, but with Dox you're involving that person's family and putting their safety at risk too, which is disgusting. Whoever doxes I hope you grow old and watch the rest of your family and friends pass away before you do and die as alone a person can be.
Child porn I don't even need to go there. Revolting. I've seen child porn 2 separate times on Twitter and it is abhorrent.
Scamming and fraud are pretty sad, taking advantage of someone else that could be vulnerable / have not much money. to be scammed is soul destroying, and the worst thing is you can't do anything once the transaction is done, and you spend about a week just at a low point and blaming yourself all the way.

Sadly dox is so common it's just disgusting. If anything would make me quit any game it would be that, my family's safety over a video game 100% every time.

Answering the OP, there's been plenty of DDoSing on Badlion (5v5 BuildUHC $1000 tournament for example) and doxing staff is fairly common too where people can be bothered to dox.