While the breakup was inevitable (especially if you read the comics), I think the show handled it phenomenally with it being even better than how it was done in the comics. Steven Yeun and Zazie Beetz absolutely killed it in this scene with you really being able to hear the heartbreak in both of their voices as Mark and Amber realize that for as much as they love each other, they can't make this relationship work. Then you have the "I can't live in your world, I want to, but I can't." which👏👏👏. That is some absolute peak writing. I haven't consumed many stories that actually treat the breakup as a heartbreaking moment for both characters involved since it's usually just treated as a minor obstacle to prevent the main romance from happening sooner. While I'm fine with that in some cases, I feel like it's a disservice when the main character's temporary love interest is a genuinely interesting and fun character who has a good rapport with them. In that same regard, it has been a nice change of pace to see characters who do care for each other attempt to make things work and talk about the issues before accepting that what they have just isn't going to work.
It's also a good commentary on the nature of superhero/civilian relationships since while someone like Debbie was able to handle the stress of it, Amber isn't able to do so. And that doesn't make her weak or a pushover, it makes her human because not everyone is built to handle that kind of life and it's totally understandable.