Woah.
Thank GOD that's only a year wasted.
'and now he's acting like a great guy'
REALLY?! 
Don't you mean to say 'acting like the childish, vindictive, silly little twat he's always shown himself to be'?
Yes, he's sent the message because he probably intends to turn up in a day or two with a half-assed 'oh I overreacted' expecting you to sigh, pick up where you left off and carry on putting up with a stupid, insincere, emotionally sub-standard little arse.
This whole pattern is classic of nasty small-time abusive wankers. They LIKE having arguments/blow up where they get to tell you aaaalllll the things that are wrong with you, hopefully reduce you to tears, then stalk off. It makes them feel good, because they are nasty.
However, they don't actually want to finish the relationship, they want to carry on the 'use/abuse/kick away/drag back' cycle.
You've said yourself he's done it a couple of times already, here he goes again. Not rocket sicence really.
Please, PLEASE stick on this thread for the good advice you will get on how to stamp him out for good.
Delete his stupid message, ignore it.
When (unfortunately it will be when) he comes back expecting you to fall at his feet, say 'No thank you. I don't want to get back together, ours wasn't a good relationship. Please leave me alone.'
He'll go bananas at that of course, because you're not supposed to have any agency here, you're supposed to be a toy he picks up and puts down when he decides to.
Tell folk you're done with him. Get support. Don't be afraid to bark right back and tell him to BACK OFF if he pushes it - you'll call the police if he harasses you.
Nasty little thing, well done on posting this.