He was predisposed to evil cuz his mom was a mentally retarded woman who had suffered years of abuse, bewitched Voldemort's smuggle father, Tom , to fall in love with her, got knocked up and stopped the enchantment, Tom ditched them, and she died.

I imagine this is what started his campaign against mud bloods & 1/2 breeds & ignited his desire for control and power.

Of course, he didn't learn of what happened to hips parents until later in life, I imagine, but I should think that just being left in an orphanage would be enough to piss him off and show those early signs. Lack of parenting, etc.