Well first of all you need to consider if you really want to break up because if you did and later start having second thoughts you might regret it.
Also the most important thing to know about us guys WE HATE GETTING DUMPED so if your boyfriend is an anger freak you ABSOLUTELY NEED TO HAVE 2 OR MORE FRIENDS (STRONG FRIENDS MAYBE COPS OR BODY BUILDERS) inside the house or somewhere else hidden when you break up because if he gets violent you need protection and also if you don't want other people to meddle with your life then please get a tazer just in case. Also if it's your house then get him to move and if not I suggest you first find a place to live before you move.
Also try to tell your boyfriend what they did make it clear to them not to ever meet or bother you and also when you break up try to be careful the first 3 months of your break up because lots of crazy people are out there and it pays to be safe.
Make him dump you. Just don't tell anyone! Trust me! Make your self seem all depressed and not wanting to talk or CRAZY or really gross. :)
If he has anger issues (NOT SAYING HE DOES!!!) just make sure that there are friends (or cops...) that are strong that can just kind of hang around outside or out of sight, and you should probably have pepper spray or a taser or something. If he breaks something expensive/lots of your stuff, you could sue.
Assuming you're living with this guy-plan ahead, if you think he will try to destroy your stuff. Wait until he is gone for a whole day or on a vacation for more than one day with someone else. Then arrange for a moving truck ahead of time and some friends to help you remove everything you own from the property. Then arrange to have a family member or friends with you when you tell him you are no longer his girl friend. While trying to do it nicely. Do not remove anything from the property you do not have proof you own. If need be have a police officer there when you remove your stuff you can prove is yours (receipts/bank statement). Also if you have anything of his leave that there/return it. Make sure you take pictures of everything you remove from the apartment/place you live and the condition of the apartment/place you live so he can't blame you for damages later. Also so there is no doubt of what you took. Remember no matter what he does stay calm and protect yourself. Even have a family member or friend record the break up if you're concerned he will be hostile. Oh! And if you're moving do not let him know where you are moving. If he needs to contact you for any reason have a friend or family member take messages and pass them onto you. So you have no contact with him after breaking up. If this house is both of your's, it needs to be sold and the proceeds should be split or he needs to buy you out.
I would say just tell him you need a "break" or make HIM break up with you.
Tell him you need a "break" and you love him but it's strange and you just need time to think about your mixed emotions. Once he's out. He's out.
I honestly think you should just sit down and talk to him. Explain why you need to leave. And let him know that you don't want to be with him anymore. When he tries to break your stuff make him stop.
Tell him how you feel, that you don't want to be with him, but if you say that he will break your stuff, when he goes to work move everything out that's your's and after just tell him and give him the apt key! Hope it works out for you.
Just say GOOD BYE. I hope you will leave along god saves you.
You should bring back up with you like your brother if you have one or friends. Don't be alone while doing it!
Try what these people are saying and if he doesn't listen change the locks if he tries anything call the cops.