Tom Hiddleston's Loki is by far one of the most popular characters in the Marvel Cinematic Universe. However, it turns out that if the original plan had been followed Loki would have gone in a very different direction. More specifically, he would have gone six feet under. In a recent interview, Hiddleston revealed that Loki's big death scene during Thor: The Dark World was originally written to be a real death scene, and not the fake out that it became. According to the actor...
If you were really taken in by Loki's death in Thor: The Dark World, don't worry, you were supposed to. It turns out that when Tom Hiddleston and Chris Hemsworth shot the scene, both actors legitimately thought they were performing Loki's final moments. Hiddleston revealed on the Empire Film Podcast that the big twist, revealing Loki has actually taken the throne of Asgard by impersonating Odin, was a twist for him as well that was created as part of reshoots.
So what happened? As is often the case, test audiences changed the game. Tom Hiddleston says that test audiences that saw Loki die simply didn't believe it to be true. As straight as the actors may have played the moment, it wasn't enough to actually convince viewers that Loki was gone. As it turned out, by believing Loki must still be alive, those test audiences actually made it happen.
Of course, from there, Marvel had to figure out what to do. Luckily, when you're dealing with a character who is an archetypal trickster, it's not all that difficult to figure out that maybe Loki faked the entire death in order to get the upper hand on everybody one last time.
At this point, it's difficult to imagine Loki dying in Thor: The Dark World. Certainly Thor: Ragnarok would have been a very different movie without him, and while a redemptive death in Dark World would have been nice, seeing him finally come together with his brother in a very real way in Ragnarok feels necessary for the character.
Also, because he's still alive, we get to see Loki in Avengers: Infinity War as well, and the more we see of Tom Hiddleston in the MCU, the better.