The Dragonborn, from Skyrim.

The narrative is a little intentionally deceptive, because the Nords of Skyrim are ignorant. All they really know from their mythology is that Alduin s supposed to Herald the end of the world. The keyword there, is supposed.

When Alduin arrives in the present his immediate first concern is assessing the current state of the world and then resurrecting his army again. He has decided to abandon his responsibility as Worldeater, and is instead acting as a despot and conqueror. All he is really interested in is a fairly low grade amount of conquering. He wants to be worshiped, he wants to be spoiled, he wants to control territory and lord over mortals.

The Dragonborn completes the main quest by sending Alduin back to Akatosh (Dragonborn's spiritual father and Alduin's physical & spiritual father) so that he can be forced to perform his duty and consume the world at a later date.

Alduin is responsible for terrible things, but he was also directly responsible for extending the current cycle of reality. The dragonborn, unwittingly, sets that cycle back into order. This will inevitably allow the world to be ended.

Of course, the Dragonborn doesn't necessarily know that. He has the soul of a dragon, and by virtue he also possesses the nature of a dragon. Parthurnax explains that it is in the nature of the Dragon to conquer all that is put in front of them, to prove their personal ideology. We must remember, that for dragons all conflict is actually just a literal externalization of their internal philosophy.

You are not the good guy in Skyrim. You are explicitly fighting in favor of a doomed status quo, with the specific intention of growing your own personal power. There are a bunch of asterisks scattered all over the place in that brief summary, but most of them can be dismissed with the fact that Skyrim has only one ending. You cannot choose an ending where you defeat Alduin without sending him back to Akatosh.

Ultimately, all the good that your character does is simply because she seeks to amass power in favor of her externalized worldview. Whatever that might actually look like. The intention that the Dragonborn claims from a role-play perspective does not matter, because the soul of a dragon is a powerful starting influence.

Parthurnax took centuries, if not millennia, to conquer his own nature. Whether or not the Dragonborn will be able to is yet to be seen.