Typically people that get called tankies defend the USSR, or China, or any other authoritarian socialist government by saying that shit was either completely made up by the west, or say that "the U.S. does it too and worse", or anything else to avoid acknowledging the human rights abuses that have happened under the authoritarian socialist regimes.

You can usually find them here in places like lemmygrad or hexbear. It's a spectrum, some people side with Russia with the Ukraine invasion others think things like the uyghur genocide in Xinjiang is just capitalist propaganda.

Here's a good example of Second Thought doing it, constantly comparing things to what the U.S. does, which obviously are bad but just because the U.S. does it doesn't mean that China can get away with it: https://youtu.be/NhPOrkGbpxk

https://en.wikipedia.org/wiki/Tankie

Tankie is a pejorative label generally applied to communists who express support for one-party communist regimes that are associated with Marxism–Leninism, whether contemporary or historical. It is commonly used by anti-authoritarian leftists, including anarchists, libertarian socialists, left communists, democratic socialists, and reformists to criticise Leninism, although the term has seen increasing use by liberals and right‐wing factions as well.[5][6]

The term originated when (iirc) Czechoslovakia was invaded by its fellow countries in the Warsaw Pact (it was also in the Warsaw Pact). Supporters of the invasion and supporters of a one-party Authoritarian State were henceforth called "Tankies".