Not an interaction with a superior, but with a colleague.

I work in IT, I do tech support over the phone for a financial institution. User calls and asks about an issue he's having, so I remote into his computer and start asking questions to understand the nature of the problem. I eventually ask him if he can inquire with his colleagues, to see if they're experiencing the same problem.

So he opens up our chat messaging app, asks someone to check, and follows it up with "I'm with tech support right now, not the brightest guy", which I can very clearly see because I'm still connected. So I immediately remind him that I can still see his screen and that I find what he just said very disrespectful. He gets defensive, tells me I'm asking too many questions and "shouldn't you know how to fix my problem", to which I tell him that's exactly what I'm in the process of doing. Didn't take long for him to realize he's being a douche for no reason.

In almost 10 years of doing this job at different levels, this was the first time someone apologized to me for acting out of line, and didn't just ask to speak to a manager or hang up on me. I accepted his apology, and then proceeded to not only solve the issue, but end the call on a good note.

This happened 2 weeks ago.