Hexbear, lemmy.ml and lemmygrad are the main Tankie instances

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

More generally, a tankie is someone who tends to support “militant opposition to capitalism”, and a more modern online variation, which means “something like ‘a self-proclaimed communist who indulges in conspiracy theories and whose rhetoric is largely performative.’” He was critical of both uses.[21] The Intercept journalist Roane Carey identified the “key element in the tankie mindset [as] the simple-minded assumption that only the United States can be imperialist, and thus any country that opposes the U.S. must be supported.”[22]

Tankies on lemmy.ml and hexbear tend to support all authoritarian communists from Stalin to Mao. They defend Russia and hate Ukraine. They defend Hamas (not just supporting Palestinian civilians but the Hamas organization too). They defend everything China does. They deny the existence of many of the atrocities committed by any country in opposition to the US.