The following is an outline of a deleted scene from the end of Captain America: Civil War
The lead-in is James Rhodes (War Machine) talking with Tony Stark (Ironman) about the injuries he suffered attempting to prevent Steve Roger's departure from Germany.
"…because it's the right thing to do. And yeah, this sucks. This is a bad beat. But it hasn't changed my mind. I don't think."
After a respectful pause, Tony segues to a different notion. "Hey I'm just realizing I may have a better option than your Robocop legs here."
"Really, what?
"You remember extremis right?"
Rhodes' reaction is wide-eyed - not where he thought this conversation was going. "I REMEMBER it, yeah - the guys with bad attitudes and the glowy arms and oh yeah the crazy one that breathed fire? The one who MELTED me out of my armor?"
Tony, of course, is caught up in the moment of scientific discovery. He completely misses Rhodes' concerns, implied by the memories of extreme violence."Yeah, that guy used to need braces to walk, most of the other glowy arm guys completely regrew limbs. The spinal cord damage here is nothing."
"Didn't you find out that - I mean wasn't the whole point - that people who undertook that treatment had an annoying tendency to explode?"
Stark can't find anything to disagree with there, and Rhodes continues:
"And explode not just a little but like very small nukes? Gary Cooper's footprints in cement at the Chinese theater were melted. It now looks like someone named Gray Cop had size 19 feet."
Still caught up in the option, Stark points out one of the results:"I figured out how to take care of that. Look at Pepper, she's fine now."
Rhodes isn't quite done, and quickly returns to the point. "And why aren't people using this all the time for amputations and stuff? How come I missed that being a radical widely available treatment for all sorts of health issues?" He considers for a second, then "I'll bet the reason isn't going to surprise me a bit."
Tony is losing his enthusiasm, but really wants to finish his point as well. "So, yes, we did get it to work on Pepper, and there are two little caveats..."
"Uh huh"
The billionaire playboy philanthropist isn't used to stopping in the middle of his proposals, even when he sees where they're going. "So first, as you might guess from Pepper not glowing in an I'm-about-to-explode way, the treatment removes all traces of extremis from the subject."
Rhodes is so surprised to hear actual good news here that, for just a moment, he's open to the idea. "That actually sounds like good news but okay. I'm sure you'd have liked to have Iron Man and Glowy Girl be a thing but she totally saved your ass then and she's fine now"
The thought of Pepper is one thing that can give Stark pause."But imagine how surprised the next group of alien invaders would be when mild-mannered Pepper Potts shows up on the battlefield…"
Rhodes completes the image: "…breathing flames and taking names."
They chuckle together at the incongruous image. Rhodes prompts Tony for the rest of the story. "Okay fine, it's a short-term, temporary treatment, what else?"
"Um - Pepper had been given extremis under conditions that AIM thought was as safe as possible since they really wanted her to survive, because it meant that I had skin in their game. But … even then there was a non-zero chance of rejection."
Ah, there it is, James is back to the real world, where Tony is proposing outlandish schemes with minimal concern for collateral damage.. "And rejection means "boom," right?"
"... Uh huh."
"So I have an excellent chance of recovering complete use of my entire body…"
Stark's enthusiasm returns: "Yeah!"
But Rhodes' is gone. "And a non-zero chance of vaporizing completely, along with everything in about a 15-yard radius?"
"… yes."
Rhodes
"Ya know, my dad wasn't much for giving advice but I'm pretty sure he would have told me 'Don't get involved in medical experiments that will make you explode.'"
"Could, COULD, could make you explode."
Which is when a FedEx delivery person arrives to say "Are you Tony Stank?"
[End deleted scene]