What Themes Make The Avengers Fanfiction Emotionally Compelling?

Undertale's emotional core is built on this wild contradiction between its goofy, pun-filled surface and its brutally sincere examination of consequences. You've got characters like Sans who crack jokes while holding onto the metaphysical weight of every timeline he's witnessed. When you cross that over, the compelling part isn't just slapping Sans into, say, 'My Hero Academia'. It's watching those other worlds, which often have much stricter rules about good and evil or life and death, get their foundations rattled by a universe where MERCY is a tangible, plot-altering force. A really effective crossover will find a character from another series who is broken by their own moral rigidity or trauma, and then force them to interact with Undertale's philosophy. Imagine a hardened Batman encountering a pacifist Frisk. The story's heart comes from that clash—can this new world learn to believe in a better outcome without a fight? Does the power of determination feel like hope or a terrifying violation of natural law to an outsider? The emotional pull is watching characters from less forgiving narratives slowly, painfully, learn that maybe they don't have to be alone, or that their suffering isn't an inevitable price for strength. It’s the hope that gets me every time, even when the story gets dark.