I Have A Strong Disdain.... For People That I Thought

I have a strong disdain.... for people that I thought I would grow out of as I got older, but it's only gotten worse.

I don't really want to see a psychiatrist as information is stored, I want this to be as anonymous as possible. I just want to know why, why do I think like this. I don't have many friends, I don't really have a desire for them unless I need something.

Additional:
I often hurt/killed animals as a child.
If someone is annoying me, I can so very clearly imagine them impaled or quartered or tortured in some form.
I believe I am currently passive-aggressive, but feel my aggressive side is slightly rearing it's head again after a good few years.
I am a 24 year old female and although I do not partake anymore, in my teenage years I got addicted to drugs, got in trouble with the law numerous times, and engaged is risky behaviour. All throughout that time. Once I came off drugs, I believe I became passive-aggressive to gain the trust of others again.
I often think of dark things regarding others and it doesn't seem to be a phase, like I thought it was in my teenage years.
It's getting frustrating. I want to know why I think like this.
I do not believe I am a psychopath though as I did 'love' my cat who recently passed away. However, I do not believe any 'love' can truly be shared between such tainted beings as humans.
If it's relevant, I didn't see my mother for 3 years when I was 6/7 years on-wards, due to an ill sibling.