I'll be surprised if anyone here remembers him, but for me, it was a Tumblr user from the early 2010s called "genderbitch". He and his other TIM friends were some of the most vile, hateful, misogynistic, narcissistic, nasty, I don't even have enough adjectives to adequately describe their depravity. Ugh!
Anyway, he would present himself as some kind of activist when all he did was sit around and grift for money and use pseudo-feminist language to talk about how He Specifically was so oppressed. He was cruel and hateful, would frequently tell women to kill themselves. Not even just TERFs; if a woman entered his askbox with "I'm a cis woman and I would like to know how to help with blahblahblah" with a genuinely well-meaning question, this guy would say "you can help by killing yourself."
And somehow this guy had a pretty large following! From what I remember, a lot of his vitriol seemed to be targeted at women of color. He also was extremely resistant to the idea that he benefited from white privilege, because "being trans cancels out any benefits I would've received from being white" or some bullshit, I don't remember.
He was so determined to twist every single situation to make himself out like the victim. Even a drunk driving accident. Yes, he caused a car accident while driving drunk, and when a Tumblr user called him out for it, asking why he didn't just crash at a friend's place or sleep in his car or not go out at all, genderbitch's response was to justify himself with one of the most insane single instances of narcissism and entitlement I've ever seen.
He said something to the effect of, "I'm glad that you're so privileged that you've never been in a situation where you were forced to drive home drunk! Unfortunately, trans women never have that luxury. We don't have the same privilege of being able to spend the night at a friend's, or sleep in our car, because we are constantly unsafe. Too bad cis shitheads like you are unable to comprehend that."
Anyway, I was already... let's say more gender-skeptical than gender-critical, but he and his cohort definitely helped me realize how their "activism" was based on misogyny and complete non-accountability, and that they were aggressively privileged and entitled just like all the other men. I came across many others like him, but he always stuck in my head as an early crazy that turned me off of the movement.