Hero is really a misnomer because your hero doesn’t have to be a hero. The term hero seems to have become interchangeable with the term protagonist when really the concept is not the same. Hero implies someone heroic while protagonist is simply the lead character in the story, arguably the term ‘protagonist’ itself implies a positive influence, and perhaps they are, from their perspective.
If we look at the Marvel films and consider the relationship between Loki and Thor then Thor is the protagonist and Loki the antagonist. Obviously there’s more to the relationship but for the sake of my word count let’s keep it short. So, from Thor’s perspective it’s his corrupt brother trying to seize power. However, if we look at it from Loki’s perspective then Thor is the antagonist constantly preventing him from taking his rightful place on the throne, throw is some sibling rivalry and a constant sense of feeling out of place and…
Whoa… Wait a minute… the villain just became the hero.
Someone once said, and damn it if I can’t remember who, that the villain is the hero of his own story and as the adage goes there’s two sides to every story. Now, obviously, Loki isn’t a hero what with his tendency to almost destroy the world and all, but that doesn’t matter, as long as you can get your reader onside and wanting to follow the character you have a protagonist. And, in the example, an anti-hero.
What makes Loki a successful antagonist is that for everything bad he does he does it with wit and flare and a charming grin. Despite his evilness people who watch the films could find themselves saying: ‘He’s wrong, but I kind of like him.’
Although your protagonist doesn’t have to be heroic he or she does have to be relatable in some way. Theoretically you couldn’t make your protagonist a complete and utter bastard with no redeeming features because the reader wouldn’t want to follow their story, they’d be repulsed by them. Though you could make the story about their inevitable downfall generally speaking these characters still have something to humanise them because it would be a select audience that could wade through an entire book or film with nothing to make them feel some sort of empathy for the character, even if it’s a case of: ‘I can see why they did it but I hope they get what’s coming to them.’
As with any aspect of fiction the only limits on your protagonist is your imagination, which shouldn’t feel tethered by the restrictions of ‘heroic’ or ‘positive’ but rather; is this who they are?