My opinion is the ending of A Hat In Time. I won't spoil it here.

In Undertale when all of your friends come to save you then get killed

It's not technically a video game, but it's based on one. In the first Pokemon movie the clone Amber Fuji dies and leaves Mewtwo all alone. I rarely, rarely cry, but I struggle to hold back tears at that part. Even thinking about it makes my eyes water.

Aunt May dying in Spider-Man PS4

The saddest moment in a videogame let's see... Probably in Final Fantasy 7 when Aerith is killed by Sephiroth. Even with the computer graphics, the game really gets you emotionally attached to the characters.

You know what? I think I will spoil the ending so DON'T READ THIS IF YOU WANT TO PLAY THE GAME!
The final boss kills some of your friends for helping you so they all realise that they can sacrifice themselves to give you infinite HP in the final phase.

When reuben died in story mode, I didn’t eat sky pork chops for dinner

I didn't even play that chapter but it was still more heartbreaking than any normal MC pet's death.

I think there is a certain way to make it so Reuben doesn’t die but I forgot what it was

when i die

He doesnt try to save pikachu
Also he comes back

Here's my saddest moment (SPOILERS FOR THE END OF HOLLOW KNIGHT). When you're fighting the Hollow Knight and he stabs himself halfway through the fight because he wants to end his countless years of pain and lonliness. Also the first two endings when you take his place to seal the radiance are also sad.

In Spiderman Ps4 At the end of the regular game not the DLC Spiderman has to choose to save either Aunt may or the city and he has to save the city instead

When Ruben dies in Minecraft Story mode. But the company is dead (Not Mojang, the other one that made the walking dead games)

Telltale Games