Todoroki is another possibility. Given his complex backstory and his struggle with his two different powers, the mask could symbolize his journey to fully accept himself. It could be a catalyst for him to merge his fire and ice powers in a new and unexpected way, or it could hold the key to unlocking some hidden aspect of his family's past that impacts his hero identity.
Kakashi could be another option. He is a highly experienced and intelligent ninja. If he came across the skull mask, he would approach it with caution. He might study it first to understand its origin and power before deciding whether or not to use it. His calm and collected nature would be a great contrast to the potentially wild power of the mask.
Perhaps the mask has some sort of hidden power that the main character discovers by accident. For example, it might be able to manipulate time on a small scale, which could be used to turn the tides in a battle or save a life at a crucial moment.
All Might could be a likely candidate. He's the symbol of peace in the My Hero Academia world and has a strong sense of justice. If he were to get the Infinity Gauntlet, he would probably use it to protect the world and keep the balance between heroes and villains. His already incredible strength combined with the power of the Infinity Gauntlet would make him nearly unstoppable.
I think the students like Kaminari and Sero would be involved. Kaminari with his goofy personality might initiate some pranks, and Sero could use his tape quirk to set up some elaborate prank setups. Also, the teachers like Aizawa could be involved. He might play a prank on the students to teach them a lesson in a rather unorthodox way. Another character could be Todoroki. His rather stoic nature could be a great contrast to the chaos of a prank.
In a darker take, even some of the younger students at U.A. High could die. This would be a very emotional and impactful event. It would show the harsh reality of the hero world and how not everyone is guaranteed to survive, no matter how much potential they have.
It could be Sasuke. He might be wearing a mask for some mysterious reason, like hiding his new powers or a new allegiance. Maybe he's on a secret mission that even Naruto doesn't know about at first.
All Might could be a likely candidate. He's the symbol of peace and the most powerful hero. Having a legendary Pokemon like Arceus would be fitting for his status. Arceus is considered the creator of all Pokemon, and All Might is like the top hero, so they could share a similar level of power and importance.
Midoriya Izuku. He's the main character and has a strong sense of justice, just like Captain America. They could learn a lot from each other, with Captain America teaching Midoriya about his combat experience and Midoriya showing Captain America the unique Quirks of their world.
Definitely Todoroki. His ice and fire powers could be used in different ways against Godzilla. He could try to freeze parts of Godzilla to immobilize it or use his fire to counter any heat - based attacks Godzilla might have. Also, Recovery Girl could be involved in an interesting way. After any battles with Godzilla, she would be needed to heal the injured heroes, and she might also come up with some unique medical strategies based on Godzilla's physiology if she could study it.
Definitely Deku. His determination and continuous growth would make him stand out in college. He'd probably be at the top of his classes, always eager to learn more about quirks and heroics. Bakugo would also shine. His powerful quirk and competitive nature would lead to some intense rivalries and great character development in a college environment. And Todoroki, with his complex family background and dual - natured quirk, would have a lot of room for exploration in college as he tries to further master his powers and come to terms with his past.