I feel like I should clarify, given some of the comments here - I don't think Marten has pent-up rage at Dora in specific. I wholeheartedly agree that it would be out of character for him to hold a grudge against her, even after everything. So when I say that I think Marten's boiling up to an explosion, I don't believe it's because he's genuinely angry at any one thing.
I think he's just sick of, well, everything.
Freud may have had a point - depression is anger without enthusiasm. That fits Marten at the moment. But if something gives him enthusiasm, if something triggers him, then it'll be anger with direction. It won't happen as easily as someone greeting him with the wrong tone, but it's so very easy for something to rub you up the wrong way far enough. Like, for example, if you've ever felt really, really depressed? And someone keeps asking you if you're feeling okay and if you're still depressed? There's pretty much nothing more annoying than that. And it doesn't even have to be one person! Ten different people could do it, and you'll snap at the eleventh. That's how it works, and if you've been in that situation before, you'll understand.
I don't want to watch Marten roast someone because I wanna see the fallout. I don't want to see him get violent and screaming and throwing shit around the room. I don't want to see him have a fit. I just... want to see that mask slip, just once, and let us see him when he's not rigidly controlling his bitterness and his feelings the way he's so obviously been doing since the breakup. And I want to see it because I love the character and this is a new facet of that character.