The TL;DR is someone who supports authoritarian regimes that 'are trying to achieve communism' to the degree that they support, often uncritically, the oppression caused by (self-claimed) communist regimes. Some examples of such regimes would be : the USSR, the Chinese Communist Party, North Korea and Russia.
They will often deny or severely undermine events such as the Holodomor, Uyghur genocide or the Tiananmen Square massacre.