One interesting aspect is the power combinations. For example, the Quirks in MHA could be paired with the superpowers of the Avengers in unique ways. Like if Todoroki's ice and fire powers were combined with Thor's lightning powers in a battle scenario.
The character interactions are also great. Imagine All Might meeting Captain America. They both have a strong sense of justice and leadership. Their conversations about heroism and how to inspire others could be really fascinating in a fanfiction. Also, the different cultures in MHA and the Avengers world could collide, like the Japanese school system in MHA and the American superhero society in the Avengers.
The plot possibilities are endless. A fanfiction could have a plot where the villains from MHA team up with some of the Avengers' villains to take over both worlds. Or it could be about the heroes from both universes coming together to fight a common, even more powerful enemy. This kind of crossover allows for a lot of creativity and new story arcs that you wouldn't find in the original works.
A practical answer is Chapter 160, because it turns the idea into a concrete scene. The chapter opens with As the sky gradually darkened, the originally mild drizzle began to..., adds pressure through Feeling somewhat guilty, she bluffed, "I—I like her, it's none of—none of..., and ends on Then.
Chapter 190 is the strongest chapter-level answer because it starts from Several people who didn't understand fell silent. and follows through on Because he saw the pack of cigarettes pinched between Jiang Li's fingers..
A practical answer is Chapter 197, because it turns the idea into a concrete scene. The chapter opens with Seeing that no one cared about what she said, Su Yinwan immediately felt..., adds pressure through Dear brother, you've protected me all this way, why not let you handle..., and ends on Wen.
The best chapter pointer here is Chapter 198, "Jiang·Deceitful·Li is Verified". It opens with He wrapped his arms around himself and stepped back half a step, eyeing... and closes on How is that possible?" "Because I've calculated it, there are no Task....
The best chapter pointer here is Chapter 181, "Are All the Weibo Followers Police?". It opens with Xiang Hao rushed to the police station as soon as he saw the trending... and closes on Let's not be too hard on a young girl.] However, these defiant words only....
Chapter 187 is the strongest chapter-level answer because it starts from During the competition, she passed by him numerous times, unfazed by... and follows through on Perhaps it was a pig that tripped you; they are quite aggressive, after....
The best chapter pointer here is Chapter 200, "Only Two Points?!". It opens with Shang dismissed the thought of turning around and walking away. and closes on Are you doing this on purpose?" Zhao Lang instantly put on an innocent....
If you want the clearest chapter reference, go to Chapter 193. Early on, Jiang Shixu's eyes lit up when he heard there was a gift.; later, the chapter leans on But the next second, he carefully asked, "Is this gift for everyone?" "No,....
A practical answer is Chapter 172, because it turns the idea into a concrete scene. The chapter opens with Not only Shu Yan, but the entire internet was shocked when they saw Su..., adds pressure through It seems Director Sun kept it quite tight-lipped., and ends on Where's the chaotic scene I was.
Look to Chapter 175 for the clearest answer. It begins with Wen Jiaojiao's eyes nearly rolled back into her head., keeps building through If you know you're sorry, why did you take so long and even redo your hair..., and lands on Su Yinwan, who had heard half his words, was a bit puzzled..