There exists 4 ways of cultivation, not systems as body; spirit; spiritual and soul, but paths inside of them. And those 4 are GOD; MORTAL; DEMONIC and EVIL.
The way of GOD is one of faith and incense the more people believe in you as something akin to a pillar for them.
The way of MORTAL is the mainstream, one there you absorb energy and refine yourself with it and make it your own.
The way of DEMONIC comes from demons often involving blood, sacrifices and the likes and is fast in the beginning and becomes slower and slower but still fast in the higher realms.
The way of EVIL is the most hated and despised in existence, since it goes against all morals and is the most deprived of them all, stealing other peoples cultivation; raping young girls/boys to get pure energy from them, eating humans, torture others for fun etc all of these is in the way of EVIL.