Tankie is a pejorative label generally applied to authoritarian communists, especially those who support or defend acts of repression by such regimes, their allies, or deny the occurrence of the events thereof. More specifically, the term has been applied to those who express support for one-party Marxist–Leninist socialist republics, whether contemporary or historical. It is commonly used by anti-authoritarian leftists, anarchists, libertarian socialists, left communists, social democrats, democratic socialists, and reformists to criticise Leninism, although the term has seen increasing use by liberal and right‐wing factions as well.

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

Typically it refers to leftists who strongly defend/advocate for authoritarian statist approaches to socialism/communism.