Izuku Midoriya had a weak quirk. In reality, his quirk was actually perfect for Heroics, but his parents preferred his sister's incredibly powerful Telekinesis quirk. Toshinori and Inko Yagi paid less and less attention to their son who's quirk wasn't as powerful or heroic as his sister's.
Izuku doesn't cry. He is a weapon, and weapons don't weep. He won't cry until the battle, when he's falling through the air, when it settles in just how real it is that he's going to die, because yeah, the doctor warned him this would happen, but there's always been a part of Izuku that thought he'd live forever. Just...