askchapo

I'm an atheist, one that was even kicked out and abused by the church and has no desire to ever join a religion again, so my answer will be surprising given that context: all of them. However, there is a catch. I'll attempt to explain.

As Samir Amin says:

Religions are not only metaphysics. They are major expressions of social reality as well. Metaphysics and social functions mix and determine each other in a continuing historical dialectic. The possible specificities of their metaphysical expression are, hence, difficult to separate from those connected to the major features of the social systems of which they are a part and which they influence.

Religions are a part of our social reality in most societies, and the key is to have religion adapt to and be influenced by the social systems in a socialist society, and not have it the other way round, where fundamentalist religious interpretations are influencing and controlling societal norms. Such a thing is obviously incompatible with communism, or any form of societal advancement. This train of thought was even incompatible with the transition from feudalism to capitalism, which is why the major religions of the time had to adapt to the changing societal norms brought about by capitalism, and not the other way around.

Modernization, secularism, and democracy are not the products of an evolution (or revolution) of religious interpretations. On the contrary, these [religious] interpretations have adjusted more or less happily to the necessities of the former... it created a new religious spirit freed from dogmas.

However it should be noted that:

There were not only "positive" adjustments, with the renovated religious interpretation opening up prospects for social transformation. There were also involutions, the religious interpretation becoming in its turn an obstacle to social progress. I will give as an example some forms of North American Protestantism.

And obviously these positive or negative adjustments towards the needs of society can apply to any religion, not just Christianity or American protestant sects of it.

Finally:

The fact that these adjustments can be positive or negative argues in favor of an interpretation of historical materialism based on the concept of "under-determination." I mean by this that each of the various levels of reality (economic, political, ideological) contains its own internal logic, and because of this the complementary nature of their evolution, which is necessary to ensure the overall coherence of a system, does not define in advance a given direction for a particular evolution.

In conclusion, as long as religious interpretations are adapting positively to the social needs and realities of socialism/communism, that religious belief is compatible with communism. However, if interpretations of a religion fail to adapt to the needs of a socialist society, or even adapt negatively towards them, such a religious belief is incompatible with socialism.

Not ones that claim that there are sadistic supernatural entities that we should worship if we do not want to get punished. And which are also weirdly fixated on subjugating women, LGBTQ people and other vulnerable groups, but are fine with literal slavery and genocides.

More generally, though, religion is fundamentally based on lies (whether the relevant claims are true or not, the people who confidently make them have no basis for those), and is, in a way, an opium for the people - a fundamentally not healthy way of coping with reality.
It can be compatible with communist movements - religion in general can be changed, as it always has done in service of the interests of the ruling class. I am not a fan, though, as religious organisations/movements' existence fundamentally relies on people uncritically believing lies and they also generally seem to support reactionary policies regarding vulnerable people, most prominently women and LGBTQ people.

On the other hand, I find this much less important than dealing with capitalism, colonialism, and imperialism. I'll take a world dominated by religion if it means that those other three points are dealt with in a good manner.

there are probably specific interpretations of pretty much any religion that are compatible with communism. i would think fundamentalism or literalism in any religion would be generally incompatible with communism. its important that any religious belief does not directly contradict any demonstrable empirical fact about reality. religion should not be a tool of political power or social control, tax-exempt status for churches is ridiculous and religious organizations need to be subjected to the usual standards of censorship for a healthy society (i.e. no promoting reactionary attitudes like nazi-ism or homophobia, etc.). it needs to be a way to increase empathy for others and to think about one's place in the world, a place of genuine intellectual engagement, rather than just a platform for an old white boomer funded by republican think tanks to rant and establish social hegemony while the hogs nod in agreement as they half-listen to his racist political screed.