Catharism
The Cathars believed that the world had been made by a bad god.  They believed that this bad god had taken them from the good god and put them in the world, but inside their bodies there was a spirit, and that spirit needed to return to the good god.  They were famous for a belief in a form of reincarnation and believed that when someone died the bad god would put that person's spirit in a new body. They believed this cycle of coming back to life could be escaped by a ritual cleansing.  They were opposed to the doctrine of sin.