Does decrying particular religions as most evil achieve anything?

Religions are frauds and should be denounced.

Only if those religions actually are doing or teaching evil things. All evil in this world needs to be exposed, and not just religious evil. There is political evil, and business evil, and entertainment evil, and a whole host more. Unless things that are evil are flagged up for the attention of people who don't think they are evil, those people will be lured in and duped by that evil, and evil will thrive, unchallenged.

At this point, it needs to be explained what evil actually is, for evil can be so subtle that it slips in under the radar under the guise of being something either good or, at least, neutral. Ask a hundred people what they think is evil and you'll get a hundred different answers. You have focussed on religions. Religious evil is taking God's good gifts then turning that into ammunition to go against God. Here's one example. Global government commissions are exposing the evil of child sexual abuse going on in many religions in the world, carried out by predators pretending to be religious, or holy, who have worked their way into positions of authority over children in order to abuse them, undetected. There is one example of religious evil, and it absolutely has to be exposed because of the way many religions are actively trying to cover up the evil deeds done by some men in positions of religious authority.

By the way, it's not a question of which religions are "most evil" - any evil done in the name of any religion is evil and God will judge all those either doing that evil, or trying to cover it up, or who are in denial about it. All of us need to examine ourselves, if we are religious, and only if we are without guilt can we then decry any particular evil in any particular religion. And if we don't, the irreligious will.

“Those who can make you believe absurdities, can make you commit atrocities.”

- Voltaire