Me & this guy were going out for about 7 months.

We were pretty serious but then he became very controlling
To where he wouldn't want me talking to my own family.

I got tired of it & broke it off we did not speak for about 2 months then he came back.

Now he's calling, texting & emailing me talking about killing me!

I already moved on & found someone new I've told him to do the same & that we can be friends..
He agreed at first but now he won't leave me alone.

What can I do to get him out my life?

Be firm, tell him you can't be friends, and leave you alone. Be sure to let everyone know he threatened you, family, friends, cops if you have to, or teachers, coaches, principles. Show them the emails/texts, if you have to.

Doesn't sound safe if he is threatening in any way and you feel uncomfortable, think about putting a restraining order on him to legally keep him away. Either that or move to another part of the country.

Tell everyone, including the authorities.
Keep record of everything.

Your safety is #1.

Save the evidence and get a restraining order, don't wait until he starts stalking you closer.