The characters might also get confused. Fanfictions often have their own unique plotlines that can be quite different from the official story. So when they see these strange twists and turns, like Thanos suddenly becoming good in the fanfiction, they'd be scratching their heads and trying to figure out what's going on.
They might be shocked. Some Avengers could be amused to see different takes on their Infinity War experiences. For example, Thor might be surprised to see how fanfiction writers portray his journey to get Stormbreaker. Others like Iron Man could be either irritated or impressed by the creativity in how his character is used in these fictional stories.
They would be shocked. The trailer might show new and powerful enemies that they haven't faced before. For example, Thanos looks really menacing. Some of them would be excited to see their new powers or weapons on display. Captain America might be thinking about how to lead the team better against these threats. And Black Widow would be sizing up the potential new allies or enemies in the trailer.
Some of them could be in denial at first. They might think it was some sort of trick or false vision. But as they watched more and more of Infinity War, they'd have to accept the reality. Then, they'd start to think about how to use this knowledge. Maybe they'd try to find a way to go back in time like Dr. Strange did in the real movie, or find a weakness in Thanos that they didn't notice before.
The Avengers would likely have mixed reactions. Captain America might be very protective, seeing it as his duty to safeguard Black Widow and her unborn child. Tony Stark, on the other hand, might initially be more concerned about how this would affect their battle strategies.
Some would be intrigued. Captain America, being an open - minded person, might be interested in seeing different interpretations of their team dynamics. He could even gain new insights about his relationships with his fellow Avengers through the fanfiction.
Some characters would likely be entertained. For instance, Loki might enjoy seeing the various ways fans write him as a more complex anti - hero. He'd probably find the creativity in the fanfiction quite appealing.
Some of them might be shocked. Tony Stark, for instance, might immediately start thinking of ways to use technology to change what he saw. Steve Rogers would probably be more concerned about the moral implications of interfering with the future.
They might be confused at first. Fanfiction can be wild and different from their real experiences.
Some students might be in awe of the power of the Avengers and the other heroes. They could start idolizing them even more. They might try to mimic the heroes' actions in their own small ways, like being more courageous in standing up to bullies at school. And for those who are more tech - savvy, they might start thinking about how they could use technology to help in a similar way to Iron Man or Shuri.
If in the fanfiction's alternate ending, Thanos is defeated early, characters like Black Widow and Vision might not have to sacrifice themselves. Their relationships with other characters would continue to grow and develop in a positive way. For example, Vision could further explore his relationship with Wanda. Also, Tony Stark might not be as traumatized, and his relationship with Pepper could progress more smoothly without the weight of the snap on his shoulders.