This sounds like a good insult/threat/comeback. "Why don't you just go somewhere and get small pox."
Another insult/comeback I like to use is "Why don't you go get lost in a National Forest?" The number is not accurate, but some believe that about 1000 people go missing in national forests each year (if you go on Missing NPF, there are currently 116 reported cases of missing people).
Another insult I like is just telling someone to fall into a ditch. It's simple, effective, implies I want you to get hurt, but not necessarily die.
Another good comeback is telling someone to "Fill your pockets." This is a reference to a Ukrainian grandmother telling a soldier to "fill your pockets with sunflower seeds, so when you lie down and die here, you'll finally be useful." It cuts deep. (also, I have not fact checked this, but even so, it works).
Acute, why do you have so many comebacks at the ready?
I have very antagonistic relationship with someone. It's all in fun, but we're always verbally beating each other up.
Anyone, thanks for coming to my TED talk.