Lelouch Vi Britannia from Code Geass. Add him to pretty much anything and you've made it at least 50% more awesome. He's the best anti-hero ever made. He is so fabulously melodramatic as well, such a badass.
The thing with Code Geass is that the entire series is one long train of "How are we going to fuck up Lulu now?" he could have the most immaculate plan, pull it off perfectly then lol jk random plot twist out of nowhere to the rescue! This happens every other episode I swear. If it happened once or twice it would be contrived bullshit, it happens so damn often it works as part of the show's charm. I'm sure the actual plot might be considered a trainwreck by some people and that might be true to an extent. However, it's such an entertaining spectacle of a trainwreck that it doesn't even matter.
I'm trying to think of an example like the OP... I got nothin' I can't think of a character I really liked in a series I really disliked. Maybe we can just add Irelia into everything for the lulz, I love that character so, so much, however the nature of a MOBA game means fuck all character development aside from the original lore
On an unrelated note, hey Riot? You know you want to upgrade Irelia's visuals next right? Screw nidalee, nobody plays her! What are you, Hotshot?
