Shepard had a bleak ending in Mass Effect, to put it lightly. Regardless of what you pick, they don't exactly get out of it unscathed. Spoilers if you haven't played Mass Effect yet, but it's on Game Pass, so get on that.
Mass Effect 3 - the original, before the remastered trilogy - had a mod that added a happy ending. It ensures that Shepard both survives and gets a hug from their romantic partner if you got one in your playthrough (thanks, Eurogamer). That mod has now been brought to the Legendary Edition.
It isn't fan fic brought to life by some talented modders who worked their way into the game's systems to create a whole new story, either. It takes cut parts of BioWare's original ending, before it turned around and said, "No, you know what, let's make this really upsetting. Give 'em a good tearjerker to send Shepard off." There's restored dialogue between Shepard and Anderson, a scene where Shepard is found in the rubble, and the Normandy crashing (again) is cut entirely.
At the end, there's a big memorial scene - instead of Shepard being among the casualties as they would have been before, they're back on their feet, putting down a plaque to commemorate Anderson. If you fancy a replay that doesn't end in sobbing, watching Shepard sacrifice themselves for the greater good, then it's available to download right now.
What's more, it supports mods that restore gay romances in Mass Effect 2, so you can have a happy, queer ending - double the fun. But keep in mind that none of it will crossover to the next game. Shepard dies in the story, but they have died before so who knows? They probably won't come back, though.
This happy ending doesn't just go beyond saving Shepard - it also ensures that the Geth and EDI survive while the Reapers are destroyed. How does that work? Magic. Let's go with magic. The Mass Relays are also not damaged, so the universe essentially goes back to how it was, albeit without the Reaper incursion. It's a true fairy tale ending.