Watching Deku get angry is like watching a dam crack before it breaks. Early on, he'd just cry or mutter, but that frustration was always there, simmering under the 'I have to be worthy' complex. When Bakugo gets kidnapped and he finally snarls 'It's your power, isn't it?!' at All Might, that's the first real fracture. It's not a clean, heroic anger. It's messy, born from helplessness and a twisted sense of responsibility he shouldn't have to carry at sixteen. That anger forces All Might to finally see him as a partner, not just a vessel, which completely shifts their dynamic.
Later, the rage during the Overhaul arc is different. It's colder, sharper, focused through the lens of saving Eri. He's not just mad at the villain; he's furious at the entire situation that created her suffering. That fury pushes One For All to terrifying new limits, but it also almost breaks him—literally. The narrative directly links his most powerful, destructive moments to his most uncharacteristic anger. It's the series arguing that his compassion has a dark, violent edge, and learning to integrate that without being consumed by it is his real growth. The 'Dark Deku' arc is just the logical endpoint of that untended rage finally taking the wheel.