After Civil War Tony is taken to the Raft and tortured. In Wakanda, T’Challa becomes concerned that Tony will share secrets with Ross and sends Steve to retrieve him. When Steve finds him Tony is in terrible shape and has been abused so badly he can barely speak. He might try to kill Steve on the way to Wakanda but only because he is delirious with fear.
When they get back to Wakanda they keep Tony locked up thinking he betrayed them. I think at one point he breaks out of his cell to go looking for a window and he runs into someone (Clint?) who didn’t realize how sick he was.
Later they realize Tony has a brain tumor (or something?) and that may have affected his choices regarding the Accords.
As much as I remember I still can’t find it anywhere. It’s not Checkmate by bobthebeekeper though there are some similarities.