Some people keep their enemies so close you can practically smell their cologne.
Strongly advise against cultivating this sort of enemy. It ain't worth it.
Conversation
I once had a guy literally follow me around for more than a year and a half trying to assassinate my character anywhere he could.
My crime? Saying something honest but negative about him to a friend of his, one time in the history of ever.
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Some people just have too much time and too little self-awareness to be worth bothering with.