A tankie is a fake "leftist" who idolizes leftist policies and ideals, but does it via worship of the past efforts, like the USSR, or even specific "socialists" or "communists" like Lenin and so many other horrible dictators... in so doing, they completely and utterly fail to live a single leftist ideal and in reality end up idolizing fascists and authoritarians like Mao. This makes them functionally identical to fascists whilst they claim leftist motives.

Tankies realize leftist ideas are good, but utterly and completely fail to connect wishes with meaningful action, thus want some power figure to do it for them. They're too stupid, ball-less, and self-centered to realize the actions they want to take are at best representative democracies, and at worst fascist dictatorships.

Tankies are wonderful to learn to properly identify, because it makes it sooo much easier to discard them and look for real leftists instead of idiots who use the same words.