Of the major religions, none of the judaism-based ones (judaism, christianity, islam, with any variation of any of the above) have ever seemed interesting to me.
I'm going to assume you mean "major" in reference to the 'Big Three' religions: Judaism, Christianity, and Islam. Other major religions include Hinduism, Jainism, Buddhism, Sikhism, and even Taoism and Confucianism although the latter two resemble philosophy more than religion. But let's set aside the word "major" as a qualifier.
The most objectionable religions combine fanatical claims of supernatural backing with aggressive proselytizing, intolerance for contrary viewpoints, and willingness to use violence. Here is one example.
George W. Bush, a Christian fundamentalist who frequently mentioned God, had the power to destroy much of Iraq and Afghanistan using nuclear weapons, but never used it. The same may be said of nuclear-armed Israel, despite being a small country surrounded by enemies bent on their destruction.
Unlike Bush and the Israelis, if the Islamic fundamentalist Taliban had access to nuclear weapons, they would not hesitate to use them against Israel, the United States, and Europe, while citing the will of God.
That's the major difference-maker in my view: for Islamic fundamentalists as heads of state, there is no such thing as restraint. All of the Big Three religions are incubators and covers for violent extremists of this kind, but in the modern era, no religion does it better (or worse) than Islam.
Ouch. I will rephrase the question if that's okay. Which one do you think is most problematic? My answer to that would be that any faith that takes on a cultist flavor in which women, children and even men are abused extends beyond the pale. As a deconverter some degree of comity is understandable, but I draw the line on what I would call severe abuse.