Get real girls......
Dear John's or dear Jane's are always done in the easiest way possible for the one who is breaking it off.
OK...it IS a cowardly way to do it but it is also a certain way to make the break clean and without rows or invective.
All you can do...( without looking for revenge as Lil Bitchiness suggests ), is to move on and get an even better and MORE fit replacement to show off under his nose.
That's not revenge, it is justice !