Ron Weasley's temper is never more raw and openly bloody than during the 'Wizard's Chess' sequence in 'Harry Potter and the Philosopher's Stone.' He's terrified, facing a giant, deadly version of his favorite game, and he has to sacrifice himself to let Harry and Hermione go on. He's shaking, but he gives the order. That's his loyalty and courage, but also that ferocious, stubborn streak—he commits to the move even when it means he might die. It’s the bloody hell moment where the stakes strip away his usual comic relief and show the steel underneath.
You see it again in 'The Deathly Hallows' after they escape the Ministry. He's wearing the Horcrux, poisoned by it, and he unleashes everything. The jealousy, the fear, the feeling of being second-best just pours out in this vicious, wounded tirade. It’s ugly and heartbreaking. He calls Hermione on choosing Harry, he mocks her crying over him. That’s Ron’s temper at its darkest—not just anger, but a deep, festering insecurity that the locket forces to the surface. It’s a bloody hell he creates for all of them.
Finally, in 'The Goblet of Fire,' when his name comes out of the Goblet and Ron won’t believe him, that cold, jealous silence is a form of temper too. It’s not a shout; it’s a freeze-out. He believes Harry betrayed their friendship for glory. That stubborn, black-and-white sense of fairness turns completely against his best friend. It takes the dragon task, seeing Harry in real danger, for that wall to break. His temper isn’t always loud; sometimes it’s the quiet, cutting assumption that hurts more.