frenemex 

a person that is classified as your friend, enemy, and ex; a person you used to date, but broke up with you, so you hate them but you still talk to at least sometimes; someone whose life you wouldn't save if they were dying, but might put them out of their misery

Friend: Do you still talk to (name) sometimes?
Me: Yeah, he's basically my frenemex.

frenemex by thegreatrandom November 2, 2020

frenemesis 

A person with whom you have a long-standing or close relationship, but who is the ultimate frenemy. An arch-rival who pretends to be your good friend, while undermining you behind your back.

She's not just a frenemy, she's my frenemesis.

frenemesis by nodramamama November 11, 2010

frenemesister

That female at work that is sometimes friendly, sometimes your nemesis, sometimes you want to strangle in a sibling kind of way.

That damn frenemesister - yesterday she brought in brownies and today she's in my office talking about office style & credenzas - I don't know whether to strangle, hug, or defenstrate her.

frenemesister by PabloNachos82 January 22, 2021

Frenemegan 

Friend+enemy+vegan: When your friend turned vegan and now is too good for you because you still eat meat. Or when you think you can be friends with someone until you realize they’re a self righteous vegan, so the friendship stalemates in the frenemegan zone.

I just spent three hours arguing with a frenemegan on Facebook!

Frenemegan by Frenemegan May 20, 2018