Having already dealt with the Frost Giants and the scheming Loki in the first Thor movie, with the latter returning with a Chitauri army in The Avengers, 2013's Thor: The Dark World saw Thor Odinson dealing with a new threat coming from the Nine Realms: the Dark Elves. But these creatures of darkness weren't always intended to be the sequel's main antagonists. According to Marvel Studios president Kevin Feige, earlier in The Dark World's development, Hela, who is debuting in Thor: Ragnarok this weekend, was originally the one lined up to be the God of Thunder's primary adversary. As Feige put it:
Hela was almost the villain in Thor 2. It didn't happen for various reasons. And thank God it didn't because now we have Cate Blanchett and Taika doing it.
Thor: The Dark World certainly would have felt like a much different movie had Hela, the Asgardian goddess of death, been the big bad. Presumably that version of Hela would have felt significantly different than the one who's being played by Cate Blanchett, though Feige didn't elaborate on the reasons for why she wasn't included. Regardless, as Feige made clear to Slashfilm, it's happy with how the situation worked out, as it allowed Hela to be featured several years later in Thor: Ragnarok under the watchful eye of Taika Waititi. It's like the old saying goes: good things come to those who wait.
With Hela off the table for Thor: The Dark World for whatever reasons, the Dark Elves, led by Christopher Eccleston's Malekith, were chosen to antagonize Thor Odinson. Using the Aether, a.k.a. the Reality Stone, the Dark Elves intended on spreading eternal darkness across the Nine Realms once again during the Convergence. Their plan ultimately failed thanks to Thor and his allies, and the majority of the Elves, including Malekith, were killed during the movie's final battle. Thor: The Dark World was met with mixed reception, though it made over $644 million worldwide.
As for Hela, she will awaken in Thor: Ragnarok after being imprisoned for thousands of years. With the help of Skurge , she will attempt to destroy Asgard by unleashing the apocalyptic Ragnarok event, leaving it up to Thor, Hulk, Valkyrie and Loki to stop her. You'll have to watch Thor: Ragnarok for yourself to judge if Cate Blanchett's Hela is a worthy villain, but the movie has already cemented itself as one of the Marvel Cinematic Universe's biggest hits yet, earning overwhelmingly positive reviews and already making nearly $110 million internationally.