To write this fanfiction, think about the backstory. For example, if there has been a recent big battle and Tony has PTSD from it. He may feel like he can't handle the pressure anymore. As for the actual jumping part, use vivid descriptions. The moment his feet leave the edge of the building, the feeling of weightlessness. And when writing about Steve, show his love and panic. He could be across town but sense something is wrong through their deep connection. After the jump, you can either have a tragic ending or a heroic rescue, depending on the tone you want to set for your fanfiction.
First, establish the emotional state of Tony. Why would he be in such a desperate situation? Maybe start with his insecurities about his relationship with Steve. Then, describe the setting. Is it a tall skyscraper in the middle of a bustling city? Next, build up the tension before he jumps. Show his internal struggle. When he jumps, focus on the fall. How does the wind feel? What is going through his mind? For Steve's part, show his reaction when he realizes what's happening. You can also add in some side characters' reactions to make the story more complex.
Perhaps Tony jumps off the building as a test. He has been developing a new suit technology that he believes will allow him to survive such a fall. He doesn't tell Steve about it, and when Steve sees him jump, he is horrified. But then Tony emerges unscathed, showing off his new tech. This causes a rift between them at first because Steve feels betrayed that Tony would take such a risk without telling him, but eventually they reconcile as they see the potential of the new technology for the greater good.
Yes, it's extremely dangerous and can be fatal. The force of hitting the ground from any significant height of a building can cause life - threatening injuries.
You can't survive. A 5-story drop is way too high. The force of the landing would cause massive trauma to your body, and it's very unlikely you'd make it out alive.
No way! Jumping off a 4-story building is extremely dangerous and almost always leads to serious injury or death.
Definitely not. The height of a four-story building is way too much to survive a jump. You'd likely suffer severe injuries or die on impact.
Yes, it's extremely likely to result in death. The height and impact from such a fall are almost always fatal.
No way! Jumping off a 10-story building is almost certain to be fatal. The impact and fall would cause severe injuries and likely immediate death.
Definitely not. The height of a 4-story building is too great. The impact on landing would cause severe trauma and likely be fatal.
Definitely. A 5-story drop has a high chance of resulting in death. The force of the landing can cause irreparable harm to your body and vital systems.