Split Lip Rayfield has some great "ex-lover" songs.
"In the Ground" is about having to kill the ex-lover because she wouldn't shut up:
"I'm sorry 'bout the shallow grave, but you're no longer that which I crave,
Now you won't wag your tongue, talkin' bout the things I've done,
You gotta love her, and leave her in the ground"
Or "The Hounds", which is a darkly humorous song about killing his girlfriend, chopping her into pieces, and feeding her to the dogs.
The hilarious thing is that these sound like hardcore or death metal songs, but Split Lip Rayfield is actually alternative bluegrass
www.splitliprayfield.com