This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Attack of the Clones
The end where a 10-year-old Boba Fett is seen picking up his father's helmet.
If you read the "Young Boba Fett" books, he (Boba) mentions that he thought that Padme Amidala was exactly how he'd imagined his mother to be. The sight of him as such a young, innocent, idealistic child, and knowing what will happen to him in the future...
Shmi Skywalker's death. She's been captured by Tusken Raiders, tortured to near death, and dies in the hands of her son, just managing to get out "I... love..." before dying. And people wonder why Anakin's so messed up. You could totally understand why Anakin would do what he did next (even though it was horrible itself) after having his mother die in his arms like that. Anakin's utterly broken plea of "Stay with me, mom." - complete with trembling jaw and watering eyes... Anyone who has ever lost a parent will know his sorrow.
But that doesn't forgive what he then does. He kills the entire tribe of Tuskens. And not just the men, but the women and the children as well. Which leads to a horrific My God, What Have I Done?.
"Across The Stars." The credits version even more so, which segues into a mournful rendition of Anakin's theme from Phantom Menace before ending with the ominous bass strains of "the Imperial March."
Obi-Wan, taken captive by the Seperatists, is confronted with Count Dooku who tells him that he regrets Qui-Gon's death and would have liked them to work together. Obi-Wan retorts that Qui-Gon would never have joined up with Dooku. His tone and facial expression show that he's furious and that even after ten years the loss still hurts like hell. So much for no attachments, ey?