Alter hates you?

One of my alters (I have only really encountered one so far, but I am sure I probably have others buried inside me) hates me and is completely ruining my life. He literally tries to ruin everything for me, one time I stupidly left the computer open when I switched and so he started to insult some of my Internet friends and make creepy sexual comments to them, which took me a LONG time to sort out. He also physically hurts me a lot, he's cut me and cut a word into my skin one time. I don't know how to deal with him and I don't understand why he wants to ruin my life. He keeps saying he wants to kill me, he even told other people to kill me... Has anyone else experienced anything like this?

Yes. I have two that hate me.

Have you asked him why he wants you to die? He might be trying to protect the body/you, or he might be upset with not having his concerns taken seriously. In my experience, alters were usually created in order to protect the person/body, they just don't have a lot of skills to deal with regular life. Another issue I've come across is that when an alter is angry it usually has to do with them needing something, and not having their needs heard, validated, and/or dealt with. Trying to understand them, and acknowledge that they are trying to help me in their own way has helped many times when my alters have been angry.
Not that this will work in all cases, but it would help if you knew all of the "WHY's", so that you can understand where this is coming from, etc.
Best,
IJ