If it's a FFA or just some random game not labelled as diplomacy, it's absolutely fine. Creating alliances in FFAs is already in gray area, breaking them is just as gray.
This is the problem. Grey.
And b/c it's grey, "it's absolutely fine" is how some people equate it. And "grey" tends to become more "white" when the benefit of doing such grey actions benefits the person questioning the greyness of it all
ie: most players equate "grey" to "white" when they are doing it (they are the backstabber), and to "black" when it's being done to them (they are the backstabber)
Just know that even if you backstab and win the game and justify it to yourself as grey/white/whatever makes you feel okay, you're still going to hell for it
Edited 7/28/2023 21:21:02