The idea that Christianity, or indeed any major religion, was "the worst thing to happen" is a thought just deeply disconnected from reality, from history and from any kind of cultural understanding.
All things that people attribute to the awful elements of religion are the awful elements of human society, or the awful elements of the human spirit. The quest to find God, which is what religion (should be) about, is a vessel for all aspects of society and the human spirit, both good and evil.
A world without religion would not be better. Human spirit would not improve in a secular world. The awful elements are still there. And in fact it probably would be worse.
I do think that one religion I personally would be fine getting rid of would be Juche. It has no redeeming qualities and is only practiced in North Korea.