Hector's face in every single scene. He knows they're on a slippery slope to hell five minutes into the film, but he can't DO anything about it (without dooming Paris) and that realization makes his entire performance just heartbreaking.
Helen being caught by Hector, almost about to give herself over to the Greeks. She knows it means certain death for her and it's unlikely to stop the war. But her guilt is catching up with her after having witnessed the funerals for all the dead soldiers.
"They're dead because I'm here."
Achilles's reaction to his cousin's death. It was his decision not to fight alongside the Greeks that spurred Patroclus to commit a desperate act of subterfuge to raise the morale of his compatriots and save more Greeks from needlessly dying in the war. He's inconsolable until the Roaring Rampage of Revenge begins.
The other Myrmidons and Greeks, especially Eudorus, are distraught as well. It's implied that all of them had known Patroclus since he was a child, and then they were forced to watch him choke to death on his own blood. Even poor Hector, who is among the most honorable and sympathetic characters in the film, looks horrified that he mortally wounded Patroclus in such a gruesome way.
The look on Hector's face when Odysseus informs him of who he just killed says pretty clearly Hector knows he's a dead man walking as well as the brief discussion between Eudorus and Odysseus making it clear Achilles's fury is going to be unstoppable.
Eudorus: We were going to sail home today.
Odysseus: I don't think anyone's sailing anywhere.
The blasé and uncaring way in which Agamemnon references the brutal death of his most prized general's young kinsman.
Agamemnon: That boy may have just saved the war for us.
The last words Achilles ever said to his cousin was not to waste his life following another man's orders. And then he rudely kicked Patroclus out of his tent. So what did Patroclus do the next day? Ignore Achilles's orders and lead the Myrmidons into battle, resulting in his bloody death at Hector's hands. Patroclus did exactly what Achilles told him and it got him killed.
Hector showing Andromache the escape tunnels beneath the city in case Troy is sacked and Hector dies. Made worse by the fact that some versions of the myth do not end well for Andromache.
Hector descending to fight Achilles. We all know how well that was going to turn out for him. And it seems his family, who are watching on, also seem to know what little chance Hector stands against Achilles. The shots of his wife, Andromache, are especially heartbreaking, as she practically has a nervous breakdown during the fight, and her reaction to his death is even worse. Also, the look exchanged between him and Helen, with Hector's look seeming to console her that this isn't her fault and that he is choosing this, but Helen still feels guilty nonetheless.
Priam asking for his son Hector's body back, especially this line:
Priam: "You're still my enemy tonight. But even enemies can show respect."
There's also his line "How many cousins have you killed? How many sons and fathers and brothers and husbands? How many, brave Achilles?" Peter O'Toole's delivery is just heartbreaking to say the least. After this speech, Achilles breaks down and sobs over the body, clearly realising the extent of his actions.
Hector's funeral has enough glimpses at the characters to make anyone cry. There's Priam, kissing his eldest son's forehead one last time; Paris standing next to him, ready to burn his beloved brother's body; Andromache, sitting up straight on the throne as she looks on, tears running down her cheeks and Helen, teary-eyed and protectively holding Hector's baby.
Another heartbreaking detail is that Hector's baby boy is holding the wooden toy that his father had been carving on his way back to Troy moments before he finds out that Paris stole Helen.
For all the Ham and Cheese in this movie, the look on Priam's face when he emerges from his chambers to find his beloved Troy in flames is utterly heartbreaking.
Briseis begs Achilles not to go and challenge Hector, insisting that he's a good man. It falls on deaf ears, and she watches him go, knowing that in a matter of hours, she'll have either lost a cousin or a lover.
And when Achilles returns, she bursts into tears, knowing that it's because Hector is now dead.
"You lost your cousin, so now you've taken mine."
Helen gives an insight into what it was like having to be married to Menelaus.
"And every day I was with him, I wanted to walk into the sea and drown."
