Let me tell you about Lexa from The 100.
So she's like...queen of the really badass warrior people who literally survived an apocalypse, right? Straight up can kick your ass (spoiler: I secretly wish she would kick my ass) and doesn't give a shit about anyone or anything.
...or so you think!
Deep down beneath that hardened exterior she's a total soft gay who enjoys being the little spoon (seriously, it was confirmed) and also likes candles and smelling nice.
So in season 2, Lexa is finally introduced after all these stupid fights between her people and the sky people. She's all "WE HATE YOU" but secretly she wants to make out with Clarke, the series protagonist. Obviously there's a lot of sexual tension, but Lexa is still kind of an ass because she only cares about the greater good and none of Clarke's friends like her.
Over the course of the season Lexa:
1. Lets an entire village get nuked so the enemy wouldn't know they had a mole in their midst
2. Kills Clarke's lover (nothing of value was lost)
3. Almost declares war against literally everyone no less than three times
and more!
So Clarke and Lexa form a tentative alliance so that they can bring down the REAL bad guys, the United States and their president (they live like mole people in a mountain and are using Lexa's people as guinea pigs). In the series finale they decide to attack the mountain but as soon as they're about to blow open the access door...Lexa decides "yeah fuck this" and strikes a deal with the bad guys. Mountain guys let their guinea pigs go and Lexa and her army won't attack them.
Clarke is obviously like "what the fuck I made out with you!!!" and Lexa is all "sorry, ur hot but I don't want any of my people to die...see ya". So now the sky people are fucked. They get inside the mountain, get captured and are being literally ripped apart by the bad guys. Clarke's only option is to straight up commit genocide, kill everyone inside the mountain (including women, children, innocents, etc) with a body count of at least 400.
Basically if Lexa wasn't a dick then there wouldn't have been a mass murder. She's still the best though.
Anyway here's a bonus video
