An equally agonizing (or perhaps even more so) scene occurs when Paul (the protagonist) is on leave and visits Franz's mother. In tears, she demands to know how Franz died and Paul lies to her, telling her he went peacefully and painlessly. In reality, Franz suffered a slow and agonizing death where he frequently voices all his regrets.
"Here is the mad tale of Detering."
The relationships of the main character. All his friends either die, lose their mind, or something! He lost everything!
"Let the months and years come, they can take nothing from me, they can take nothing more. I am so alone, and so without hope that I can confront them without fear."
Considering that, the ending is the best thing that could happen to the protagonist. Which doesn't make it less of a Tear Jerker, but the rest of the book is From Bad to Worse.
Especially the part where he comes back home and sees his books, his writings, everything he was... and realizes it doesn't move him at all, because he isn't that person anymore, and never will be. He finds he can no longer even relate to his family, whom he was very close to before. His mother is the only person who he feels still understands him and she's bedridden with illness.
Kat's death. "You are not related, are you?" No, we are not related. No, we are not related. Do I walk? Have I feet still? I raise my eyes, I let them move round, and turn myself with them, one circle, one circle, and I stand in the midst. All is as usual. Only the Militiaman Stanislaus Katczinsky has died. Then I know nothing more."
The ending. "He fell in October 1918, on a day that was so quiet and still on the whole front, that the army report confined itself to the single sentence: All quiet on the Western Front. He had fallen forward and lay on the earth as though sleeping. Turning him over one saw that he could not have suffered long; his face had an expression of calm, as though almost glad the end had come."
This is followed up by a shot of a field of crosses, overlaid by a shot of the German soldiers marching off solemnly. This may be perhaps the definitive War Is Hell shot.
This is from the 1979 version. Our protagonist is defending his trench in a nocturnal attack by the French, and manages to cower away in a crater. A French soldier jumps into the crater and Paul manages to wound him, but not kill him. During the remainder of the night and some parts of the day, the French soldier wails in pain and Paul unable to do something. First, he tries to kill him with a dagger, but he's not able to go in for the kill. Then he tries to patch him up with a roll of band-aid, but then he dies in front of his eyes. Totally stricken, he monologues that he didn't wanted to kill him, excusing himself for the French soldier and going even as far as saying that he's going to write to his family at home. He doesn't do it in the end, but the sheer fact that he's bawling at the death of an enemy soldier made me go shed my tears after watching the movie.
(1930 version) Do you know how demoralising it is for Paul to visit his old classroom and have idealistic young students call him a coward?
Paul Baumer: [angry] I've been there! I know what it's like!
It's even more upsetting to know how solemn he first appears, before erupting into a distressing tirade of indignation when his ex-professor and the new students object to the horrors he's seen, even though they've never experienced it themselves. His friends are dead and he's seen things he never wanted to, so he's got every reason to find so much offence at what he's hearing.