(Source: https://nerdist.com/thor-loki-encounter-hela-first-time-ragnarok/)
First of all, I am so glad to be able to include Hela in this list. Because there was the danger of her not being interesting or noteworthy at all and at the worst a sexy seductress. Don't get me wrong, she is plenty sexy (everytime she was on screen, you could hear me whisper 'I'm so gay'), but that's not what she is about.
Spoiler Warning for Thor: Ragnarok!
What Hela (Cate Blanchett) is about, is war and conquest. Imprisoned by her father Odin (who continues to be the absolute worst father in the history of ever) when he couldn't control her anymore, she is now, after his death, back with a vengeance. In earlier days when Asgard was young, it wasn't peaceful at all. Odin and Hela conquered worlds together and waged war together. And all she wants esentially is to restore Asgard to its old imperialist glory. But Odin has - quite literally - painted over that past and Asgard's populace is not willing to help her with her plan. So she kills them. Simple as that.
As is typical for Marvel villains she is rather one-dimensional in her murder happiness and doesn't have the most complex motivation. She is, however, strong enough and a big enough danger that the only thing that can stop her is the apocalypse.
Another thing I like about her is that through her being the resprensentation of aggressive imperialism that can only be defeated with the destruction of the previously imperialist nation, the movie is notably anti-imperialist. Nice.
