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Tear Jerker: The Last Spartan
A rather small yet still powerful one occurs in Chapter 26, Garrus and Master Chief get into an argument over Tali almost finding out about Cortana. Garrus tries to pressure Chief into revealing Cortana to the crew, believing that they wouldn't rat him out because they practically revere the guy as a hero, while Chief continues to disagree. A intense argument between the two occurs that keeps building up and up until finally the Chief breaks his normal stoic attitude by practically yelling at Garrus, while almost preparing to hit the Turian. He then finally cracks open and mentioning all of his friends, practically the closest thing he had to a family are all dead. And all he has left is Cortana, and can't risk the Council taking her away.