When they were in space together, Nebula and Tony became close. They had to, being they were the only living things around. He taught her how to play finger football and she cared for his wounds. One day, about 10 or so days in, she asked an important question.
“What happened to you?” Nebula asked.
Tony scoffed before answering, this time without his usual mask of sarcasm and uncaring. He spoke, his voice rough from the depleting oxygen.
“What hasn’t happened to me? I’ve been kidnapped more times than I can count, including a 3-month vacation in Afghanistan where they were paid to kill me. I ended up having surgery in a cave to take shrapnel out of my heart. Yinsen,” his voice broke on the name, “tried his best to get it all. He also helped me put the arc reactor in my chest. He died protecting me and told me to not waste my life. A bunch of other bullshit happened like Palladium poisoning and the Avengers were formed. I wasn't even supposed to be one, but they decided they needed the billionaire. Then I flew a nuke into a wormhole Rogers wanted to close with me in it. Then I was mind-controlled by Maximoff, which gave me the reason to make Ultron. Which killed my first AI, JARVIS. And yeah, that was my fault but it was also Bruce and Maximoff. And Maximoff's brother died protecting a little boy and Barton. She hates me for something I didn't control, the fact that someone I trusted double dealt weapons under my nose. And don't even get me started on the fucking Accords." And he kept ranting to her. He had to stop to save oxygen, but eventually, he got everything out.
Including him hiding his parent's death and leaving him in the Siberian bunker to die. He also confided about Peter Parker and how he feels guilty about his death and how he loved him as a son.
Day 22, just when he was about to run out of oxygen, Carol Danvers aka Captain Marvel came to their rescue. She brought the ship back to Earth. The 2 had become even closer. She was actually calling him "Tony" and he would call her "Neb" or any of the many nicknames he had.
When they walked off with her carrying him slightly, she asked him which one was Steve Rogers. When Tony pointed him out to her, she carefully transferred him to Rhodey and Bruce, before rolling up her sleeves and walking towards the man who hurt her friend.
"NebULA NO!" Tony yelled out when he saw her, but she paid him no mind, striding right up to Steve and punching him in the nose.
He screamed out in pain and grabbed his nose as Tony looked horrified. Rhodey, Bruce, and Pepper all looked smug seeing the man who hurt their friend. Steve looked hurt and confused but Nebula just looked content with her "work".
"That is for Tony."
She turned around and walked back to Tony while the others were trying not to laugh at Steve’s pained face.
“Neb, you didn’t have to do that,” Tony told her softly.
She looked at him, showing the softest look he had ever seen from her.
“Yes. Yes, I did. You are my...friend and I...care about you.”
He smiled at her and hugged her. She hesitantly hugged back.
“We’ll get them back.” He whispered in her ears.
“I know.” She whispered back. “I know.”