What would you consider a significant reason to instantly end up relationships?

As for me, I find it disgusting to see my girl sleeping with another guy. I've never been in this kinda situations before, but just knowing this fact will make me act instantly.

Intimate discussions with a guy other than me, sharing me naked with her friends on her phone, sleeping with a guy, stealing, insulting my family, abusing kids or animals, freeloading... to name a few