I'd say that for me, personally, cheating is an absolute termination of relationship issue; you may feel differently but I'll explain my reasoning in case any parts of it are helpful.

The first thing is I'm a Relationship Anarchist as a result cheating on me is really, really hard to pull off. I don't set boundaries and expectations on my partners except for those around our dynamic and safety (e.g. "hey, if you do it unprotected off-set tell me so we can be careful until your updated results are available in 3 months."). That means pretty much the only way to cheat on me is to do all of the following at the same time: - Have a relationship with another person - Intentionally lie about your intentions around that relationship or deliberately conceal it - Lie about the nature of that relationship intentionally - Deceive me about how that relationship has been affecting my relationship with you

That takes a pretty significant level of dishonesty.

Ultimately after an intentional betrayal like that it's not going to be possible to rebuild the trust needed for me to feel emotionally safe with a person again. Since I have a power exchange fetish, and I'm Aromantic spec. grayromantic, I need to be in a D/s dynamic to feel that connection to someone. Since I can't feel safe with someone who cheats on me I'm just never going to be able to maintain a dynamic with them again, that trust is just too damaged.