Religious extremism specially Abrahamic ones because they(all) believe in gospel truth, Despite all the evidence. They also want to enforce laws based on gospel truth. While greedy can be reasonable.

Greed as in people that abondon all morals for material and money.

Its called materialism and is related to Philistinism

Schopenhauer defined philistine as

he is a human being without intellectual needs. Several things follow from this: first, in respect of himself, that he remains without intellectual pleasures, according to the already mentioned principle: ‘There are no true pleasures without true needs.’ No keen urge towards knowledge and insight for their own sake animate his existence, nor one towards actual aesthetic pleasures, which are definitely related to the first urge. Such pleasures as are imposed on him by fashion or authority, he will dispose of as quickly as possible as a kind of forced labour. Real pleasures for him are the sensuous ones alone; in them he finds compensation. Accordingly, oysters and champagne are the highpoint of his existence, and the purpose of his life is to acquire everything that contributes to bodily well-being. And he is lucky enough if this purpose keeps him busy! For if those goods are already conferred on him in advance, he will inevitably fall prey to boredom, against which all possible means are tried: ballet, theatre, society, card games, gambling, horses, women, drinking, travelling, and so on. But all of these are not sufficient to ward off boredom, when a lack of intellectual needs makes intellectual pleasures impossible. Hence a dull, dry seriousness, close to that of animals, is characteristic of the philistine. Nothing delights him, nothing excites him, nothing rouses his interest. For sensuous pleasures are soon exhausted; a society made up of philistines just like him soon becomes boring; card games finally become tiresome. At most, he is left to enjoy the pleasures of vanity in his own way, consisting in his exceeding others in regard to wealth, or rank, or influence and power, by whom he is then honoured, or in associating with people who excel in such things and thus basking in[366] the reflection of their splendour (a snoba). – From the fundamental qualities of a philistine we have described it follows secondly, in respect to others, that, since he has no intellectual, but only physical needs, he will seek out the person who is able to satisfy the latter, not the one who can satisfy the former. Hence among the demands he makes on others, the least will be that of predominant intellectual abilities; on the contrary, if he encounters these, they will arouse his dislike, even his hatred, because in reaction to them he has only an annoying feeling of inferiority and, in addition, one of dull, secret envy. This he carefully hides by trying to conceal it even from himself, which is why it sometimes grows into a secret rage. Therefore, it will never occur to him to measure his appreciation, or deep respect, in accordance with such qualities; this is exclusively reserved for rank and wealth, and power and influence, which in his eyes are the only true merits in which he wishes to excel. – But all this follows from the fact that he is a human being without intellectual needs.

This question is separating one and the other - both are bad - but I think religious extremism is powered by extreme greed causing extreme poverty and vulnerability.

So actually, maybe I do have the answer. Get rid of extreme greed, and religion does not go extreme.

Even the crackpots calling for genocide won’t get a voice.

Correct me if I’m wrong but even Hitler employed the tactic of blaming the Jews for the poverty (and other things) in Germany. But in reality it was the Great Depression. Germany was one of three nations that had the highest unemployment in the (western) world.

Yes, Nazism wasn’t a religion but a cult. But religions can involve a god, many gods, or idolise an object or a person. Hitler was it. He was like a war god.

I would rather religion doesn’t exist any more, not just religious ‘extremism’, that sounds very subjective

Both religious extremism and greed are superstructural, not the base. Leftists target the base, as the superstructure is shaped by the base and in turn reinforces the base. Move onto socialism and communism, and the oppressive superstructural elements of today will also fade.

The priority for me is any authoritarianism. Authoritarianism by itself is extremist; wanting a world liberated of that is not.

Surveillance capitalism, religious fundamentalism, it’s all the same to me: they seek to control people and the flow of good life standards, away from the masses, towards their leaders.

Surveillance capitalism does so by selling your private data to the highest bidder, and these will use it to spy on you, bribing, harassing, and corrupting lawmakers into creating a surveillance state - a perfect recipe for authoritarianism to pop its head up. They direct attention away from the oligarchs so that we do not combat them.

Religious fundamentalism sells your personhood to the strongest converters, to those that strip you of autonomy; such groups thus also spy on you. They always look for the downtrodden, weakest and most vulnerable, to direct their hatred for their current situation away from the true source – oligarchs.

So for me, I’d say there is no difference and this question is meaningless: it’s asking for the difference between a golden apple/window and a golden cross. At the end of day, both cannot be eaten, but all buy it up blindly.

Greed 100%. Religious extremism only hurts a minority. The people trapped in the cults, the family members of the 50’s dad hitting them with the bible, victims of crusade/jihad style atrocities etc.

Which is awful but manageable.

Greed is definitely, definitely definitely going to end our entire species, probably only a couple generations away.