I'm new here and I'm 100% sure I have anger issues.

I get overly angry at everything and when I do it leads to more arguments and fights. None physically, except between me and my sister who is a year older than me. We fight almost all the time and just 30 minutes ago we fought over a silly thing like the Xbox controller and I said that she could go kill herself once I got in my room, separated from her. Am I a bad sibling for saying something like that over a little thing?

I don't think you're a bad person . I fought a lot with my siblings when I was younger , mostly over stupid little things . I remember hating them in those moments too . I'm much older now and those days are gone . We still argue or fight sometimes but it's not an intense emotional experience and I don't feel hatred or want to hurt them in any way .

You showed a lot of good self-control by leaving the situation before you said something hurtful that you might regret later . Anger is powerful in the moment - that's when we can do the most damage to another person . I think you used very good judgement , even though you were stressed and angry .

Hehe, I have an older sister, and while we were living together, I tried to strangle her more then once.
The moment she moved out of the house, she became my best friend.
You made the right call by stepping away. Being that close all the time means that whatever frustrations you have, you share.
Siblings are SUPPOSED to drive you up the wall!
You have a bond that can never be broken, so you can say things to each other that would break any friendship.
Right now, you are like two puppy dogs, competing for mommy's milk, forced to live in the same kennel.
As you mature, you will each become your own person, and much less dependant.
Remember: before things escalate, step away.

Before it gets even worse follow this steps instead:

Think before you speak. In the heat of the moment, it's easy to say something you'll later regret. ...
Once you're calm, express your anger. ...
Get some exercise. ...
Take a timeout. ...
Identify possible solutions. ...
Stick with 'I' statements. ...
Don't hold a grudge. ...
Use humor to release tension.