I've got two that I could think of.
Cr1tikal
Already mentioned earlier in the thread but it really was lame to see him drop off. Back in the day before the face reveal, he was like a hidden gem. He got a lot of views but I didn't see any other YouTuber ever mention him and just happened upon him, his videos were hilarious and his deadpan reactions to an awful horror game or random obscure shit I never seen anyone else play was great. First time I ever seen him mentioned by someone else was during the Fine Bros controversy over them trying to get the rights to the word "React", where I think Keemstar mentioned his video on it in his video. Not long after that was mentions of him having a Snapchat and that's where his face reveal was, then the official face reveal video on his channel. After that it just slowly went downhill, mainly around 2019. As for the video that made me stop watching him, it was his awful response to the iCuckzzz drama, where he called people incels for caring about Ian being a cuck, while he himself shit on ProJared for his fiasco. There was also his EDP445 video where iirc he said his name aloud and was like "Really? Naming yourself Eat Dat Pussy?" or something along those lines, lacking complete self awareness to the kind of jokes he spouts every video. Then he donated to BLM during 2020 and became a shitty react streamer, always hunched over and sounding bored with life, what a bummer. Also not related but he doesn't look good with the super long hair. He used to have a nice haircut, then he grew it out to a mid 2000s emo hairstyle, now he looks like a greasy hippie. It's ridiculous people compare him to Jesus.
Pyrocynical
Also mentioned in this thread, the video being his controversy about doing weird sexual furry roleplay with a minor on Discord. It's baffling people forgave and forgot all about that almost immediately yet CallmeCarson got cancelled to oblivion over a 2 year age gap. No one also brings up how he tried to bring the minor to the UK and wanted to get him a fake ID to get into a bar, where I'm sure he wouldn't have tried anything right?