This is actually a serious question although I could have asked it a little nicer, I just didn't care to. *shrug*

I tend to think there are two causes:

Inherent and conditioned

Often, these two go hand in hand.

Inherent is genetic. There are gentic conditions that are passed down at birth. These are unavoidable

Then there are conditioned that are learned through example and environment.

Because of the genetic factor, you will find the environment one is raised in to foster the behaviors because the parent doesn't have any other resources to pull from.

You will find, also, that a lot of people who have become serial killers have had a significant blow to heead. While not proven as causation, it is a very common event and it is known that severe head injuries can change a personality.

I bring up serial killers because a lot of them would torture animals, knowing it was causing pain but would do it anyway. This, to me, illustrates that people do intentionally inflict pain, whether physical or emotional, intentionally. They know they are doing it.

One of the best lines I have heard about narcissists is:

"Do they treat every one the same? No. That means, they know on some level what they are doing and are choosing to do it."

I believe there are genetic or biological predispositions that can be either mitigated or exacerbated by experience or environment.

For example .. there is no cure for narcissism. The inherent nature of the disorder can make effective treatment a real challenge for many. However, some are able to affect meaningful improvement if so motivated.

I definitely believe a small bit of people are indeed born really messed up. The same way we can be born genetically "flawed" in other ways I don't think it's too hard to fathom that someone could simply be wired wrong. There's some people who think of themselves singularly without consequence of how the things they say and do effects anyone around them.

On the other side of this, there are those who have been bred into such things or learned to adapt to it to get by because it gets them what they want and they see that it works. Either by having to survive that way, never being given rules and consequences, etc and several other things. There's so many variables.

Not really sure people are born being horrible people.
I think they're born with some tendencies that if they conditions are right ,they're never checked or taught to control impulses you get some real messed up people.

I think it’s from life

Both. I think very few are “born bad”. The vast majority are the result of their home environment.

At the root of it, I think we all have this seed of darkness or whatever you wanna call it, and the only difference is how dominant it is as to how much life experience is needed to activate it and how fast and high it can grow.

I blame it on there parents usually.

Life & experience does shape people but if their core is rotten it's hard to fix them

Some people are just born with the inability to think of anything/anyone except themselves.