This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / The Phantom Menace
Qui-Gon's death after the battle with Darth Maul.
That he tells Obi-Wan, who he has a father/son relationship with, to train Ani when he obviously wants to say something different is another one. The way he gently brushes his tears away is heartbreaking.
Made even worse when you realise that Obi-Wan freaking knows that Qui-Gon is losing the fight. His expression goes from anxious to terrified during the sequence.
Before Anakin left Tatooine, he asked his mother if they would meet again. Those who watched the following film know that they will, but under very painful circumstances.
When Anakin had to choose between his life on Tatooine with his mother or following his life dream of becoming a Jedi Knight. Made even worse that he eventually turns Sith.
What's worse is that he sees the Jedi as the ultimate saviors, out to free the slaves on Tatooine and virtually unkillable. That myth he holds on to slowly crumbles over the course of the film as he finds himself initially rejected by Jedi Council for simply being too old and later on, after the Battle of Naboo, learns that his Jedi father figure Qui-Gon was killed by a Sith Lord. As the next two films reveal, it only goes downhill from here.
Qui-Gon Jinn: Perhaps I killed a Jedi and took it from him.
In the deleted scene introducing the podracers on the grid, we see the commentators introducing racer Ratts Tyerell and his family, including his newborn child. One lap into the race, he was killed when he crashed into a stalactite. Cue the tears of sympathy for his family when you realise that his family was likely watching the entire incident take place. Shmi states earlier how much she hates it when Watto makes Anakin race. No doubt she's terrified of watching something like this happen to him.
Shortly after the Senate meeting, the Queen is dressed in mourning wear and looking out the window. The look on her face is hard to watch as she knows that the longer she sits there, the more people on her planet are going to die. Even Jar Jar, arguably the most hated character in the Star Wars mythos, looks concerned.
Jar Jar: Do you think yousa people is going to die?
Amidala: (mask just slips) I don't know.
Jake Lloyd, the actor who played young Anakin, said that the other kids teased him so much after he starred in the movie that he later burned all his Star Wars memorabilia. Knowing that the kid who portrayed Anakin as a sweet, helpful boy was teased and bulliedfor it in real life, is hard to stomach.