What would happen if a person signed a paper saying they wouldnt do something and than did it?

Depends if you can get an atty to prove the person is breaking a contract--- you can always go on Judge Judy!

they will burn in hell for ever and ever.

depends on what you signed and if it was truly legally binding

Nothing. A piece of paper means nothing when it comes to a persons emotions and feelings. Like when people get married. Marriage is a contract - thats why you have to go to court to get divorced. It is a legal binding contract that you agreed to do something.......Good Luck

Technically you are breaking a contract.

If the contract defines penalties, you will be liable for those.

If the contract does not define penalties, you are still in violation, but it will be challenging to have the court decide on what the penalties should be.

In either case, if its a "big deal" contact an attorney.

Depends on the paper, is it a contract or some kind of legally binding document? If so call a lawyer & ask about it.
If not, then there's not much you can do. What is the person doing & what did they sign?

I guess someone would be angry at them