Upvoting for helpful discussion. I think the word you could be looking for is leftist, though I'm no expert.

What I do know is that tankies, highly ironically, only pretend to be leftists, while actually denying reality itself. Some Trumpists are this way on the Alt Right as well.

One short definition of a tankie is that they deny what happened in the Tiananmen Square massacre, specifically they don't believe that anyone died (or variations thereof), despite literally all evidence including videos and statements of people who were literally fucking there first-hand. Again there are counterparts on the right as well e.g. the holocaust deniers, and the similarities are striking.

A defining characteristic of a tankie instance, for me, is not the source of their political viewpoints and rather the hostility and toxicity that they spew forth onto others with seemingly no regard for things like "consent". It's a zealous mindset that ceases to question one's own beliefs and rather feels entirely justified in unleashing whatever vitriol they choose onto others. So I guess I need a better word then than "tankie" for that:-).

So leftist != tankie, bc ironically tankie != leftist.

Relevant post