WARNING: Spoilers Off applies to this Tear Jerker page. All spoilers will be unmarked. Read at your own risk.
The scene pictured, when all the Earth Engines ignite for the first time and begin pushing Earth on a 2,500-year long journey to another star system. After five billion years, Earth finally leaves its home forever, leaving behind its moon and its neighborhood. These things will never be seen again. This was not an easy decision to make, by any means, but for the sake of continuing life on Earth, it was necessary.
Liu Peiqiang: Since the day that the Wandering Earth Project was started, there was no turning back.
Han Zi'ang's death. Trapped in a collapsing building in Shanghai and losing oxygen through the rip in his suit, he accepts his fate, sitting up in a chair and removing his helmet to take in the little air of his hometown one last time. As his face freezes, he remembers how he saved Han Duoduo as a baby during his time as a rescuer (itself a tear jerker), and expresses hope that Liu Qi will take good care of his adopted little sister, before the building finally comes down.
Han Zi'ang: Hu Kou. As a brother, you have to watch over your sister. Take Duoduo home...
Makarov's death. After deciding to join Liu Peiqiang in infiltrating the Navigational Platform International Space Station's control room, he encounters numerous difficulties, crying for his mother and screaming how he doesn't want to die. Eventually, upon reaching the control room, MOSS decides to activate a thruster in his face, cracking his helmet. He can only close his eyes and accept his fate as his helmet shatters and sends him into space, but not before giving Liu Peiqiang a final push to reach the control room.
Makarov: Liu. I do believe in your words. There will be a day when ice turns into water. That's when we will take our children to go salmon fishing.
Just the idea that the Earth will be destroyed by Jupiter itself is a tear jerker. Not only does it mean the death of almost the entire species, the loss of the humans' entire homeworld, and the destruction of everything that anyone ever knew, but it also means that the Wandering Earth Project had failed too soon. Only seventeen years into the 2,500-year journey, the project ends in a disastrous failure that doomed the world faster than the dying Sun did. This desperate plan by a tiny sentient species had so much potential and was filled with so much hope, but was ultimately not meant to be. Fortunately, of course, the humans were able to scrape together a second chance.
MOSS's announcement to the world that Earth was on an inescapable collision course with Jupiter and that it was futile to attempt anything else, as it encourages the people on Earth to make the most of the time they have left. Meanwhile, the people on Earth are despairing and rioting, and we get to see a Kid Amid the Chaos.
He Lianke, who sees a note from his mother to keep warm while he lights a cigarette. After getting buried under rubble while trying to manually override the controls for the Earth Engine, he musters up enough strength to make the final connection. He then gives a thumbs up to Li Yiyi before dying.
He Lianke: Life and death are normal.
Of course, Liu Peiqiang's death. With Jupiter's atmosphere just out of reach of the Earth Engine's amplified exhaust beam, he makes the decision to pilot the Navigational Platform International Space Station into the stream to cause an explosion big enough to ignite it. Liu Qi screams at him not to do it, before Peiqiang finally calms him down by calling him "son", and apologizes for having to break his promise to return to him. However, he recites something that he told Qi in his youth: that all he needs to do is to look up.
Liu Peiqiang: This time, I promise you'll be able to see me. Come on, son. Three. Two. One.
Wang Lei is unable to escape from the rubble he is buried under and dies. However, before he dies, he gives his rescue team a final command.
Wang Lei: Members of rescue unit CN 171-11. Attention. This is an order. Live on.