Mantis wouldn't feel guilt from Tony if she touched him
Apparently in this story, Mantis touches Tony and feels "all the horrible guilt" he suffers. The interesting thing is, Tony doesn't seem to feel particularly guilty about anything. His Iron Man epiphany was mostly about how he himself was harmed, not the harm he did to others. After all, he didn't really stop making weapons, he only started keeping them for himself. And he didn't part with a single dime of his multi-billions to help any of the victims of his weapons through the decades he was in charge of Stark Industries. When he says "Ultron, my fault," in Civil War, it's a throwaway line. If he really felt any guilt, he would have admitted his part in Ultron's creation publicly and accepted the consequences. Or cared about the dead Sokovians, not just the random American who died there. And Tony wouldn't have claimed that his suit of armor around the world was worth people losing their "precious freedoms" just two films later.
What would Mantis REALLY have felt if she touched Tony?
Note: I haven't seen the GoG films so I don't know if Mantis would really hear Tony's inner monologue, but she can here.
***
Everyone was tense as they waited for Thanos to arrive on Titan. Drax was pacing--he took one step, paused for a minute, then took another step. Peter was flipping his gun around. Dr. Strange was strangely floating in the air with his eyes closed. The Web Boy was climbing the stone structures nearby while Nebula watched. And the Iron Man...
Mantis looked at the Earthling as he grumbled to himself about plans and who was really in charge. Unlike the other two passengers, Mantis was uncertain about the Iron Man. He seemed as cold as his armor, and just as shiny-hard. He just didn't want to listen to anyone's opinion but his own.
She knew that a shallow exterior sometimes hid depths of warmth and wisdom. She'd learned that in her time with her fellow Guardians. And normally she didn't use her powers without desperate need or actual permission, but she had to be sure.
The moment Mantis rested a hand on the Iron Man's head, she knew she made a mistake. The salty, petty bitterness in him overwhelmed her own sense of self. Because the Iron Man was ALL about himself. How HE knew better than anyone what to do. How HE should be seen as the natural leader because goddamn it he was a billionaire-genius-playboy-philanthropist. How everything would be fine if Cap and the other rejects had just listened to HIM and did what HE SAID--even if what he DID was the complete opposite. How could they BETRAY him like that and ABANDON him with just the stupid kid who needed to keep his mouth zipped and do what he was told. NO ONE understood HOW MUCH he suffered and HOW HARD IT WAS being Tony Stark and Iron Man and the savior of the world and too bad Ultron wasn't working because that would have solved EVERYTHING because everything he created was wonderful and--
Mantis jerked back and took a few deep breaths as she tried not to throw up. She looked at Nebula and said, "I think we need to reconsider."
***
The Guardians left Titan before Thanos arrived, so Thanos had to go to Earth to get the Time Stone. With Dr. Strange safe behind the Wakandan shield, he protected Shuri and Vision while Wanda was out in the battle from the beginning. With the extra firepower of the Guardians, Spider-Man, and Dr. Strange, Thanos and his forces were able to be defeated. When Thor arrived, it didn't matter that he didn't go for the head--because Nebula and Peter Quill did.
Tony wasn't part of the battle. When the ship landed on Earth he decided to go sulk in his Tower. He wasn't needed anyway.