Christianity.
Islam.
Buddhism.
Jewish.
Protestant.
Catholic.
Sikhism.
Scientology.
Mormon.
I hate them all for various reasons. Christianity destroyed both my of heritages. I am Cherokee-Irish(Erse).
It all but wiped out my religions, my languages, my histories, my cultures.
So here is how I would personally rank them as the worst.
1) Scientology- because it is a scam of the first magnitude. It enslaves people to this day and steals their wealth and youth.
2) Christianity- for committing genocide and destroying cultures.
3) Islam- for forcing people back into the 5th century and the baggage that comes from the dark ages.