If you are the partner who might want to issue a veto, consider stating boundaries for yourself instead. You could say, "This situation is degrading my happiness to the point where I can no longer imagine being happy if it continues. If you keep going down this course, I won't be able to remain in this relationship." Indeed, it's an important part of consent: you always have the right to withdraw consent, for any reason. You never have to remain in a situation that hurts you.
