Eruri in some kind of domestic AU, I think the one who always yells and swears a lot while angry or mad at his partner is probably Levi. Erwin will just listen to him, wait until he finished, and apologize afterwards while holding his hands, sometimes gives Levi a hug to soothe his partner.
And Erwin? He will use a very polite language, look at Levi right in his eyes, maybe ask Levi a few times to look at him back in the eyes when he noticed Levi averted or looked away from him, and just that Levi will apologize quickly because it’s Super Effective kind of terrified him.
That was probably the moment when Levi lost his shit and realized that he should never make him angry.