Every protagonist should have at least one Key Component that defines them as the person they are. Often several exist, but you need at least one dominant Key Component that sets your protagonist apart from the rest of the herd.
Superman’s Key Component is that he values life and never kills (as well his classic motto of ‘truth, justice and the American way’ attributed him in the 1940s that DC has since changed to ‘truth, justice and a better tomorrow’ while pandering to unpatriotic Social Justice Whiners who hate the freest country that gives them every opportunity in their enabled lives). Any comic book nerd can tell you that, which is why we had such a problem with Superman snapping Zod’s neck at the end of the 2013 Man of Steel movie. Other options existed to thwart Zod from murdering those innocent people with his blazing eyebeams, and Superman killing Zod goes against his character. Remove this Key Component and he stops being Superman.
For example, the 2019 movie Brightburn. The filmmakers just took Superman, made him a child then removed his Key Component. What we have left is a boy with Superman powers and no compunction about using them to hurt or kill people.
Batman also shares this Key Component because Batman never kills. Heck, he will even risk his life saving a bad guy from certain death even though he was beating the crap out of them ten seconds beforehand. Another Key Component of his is that he never uses guns because as a child he witnessed his parents shot to death during a robbery in an alley. But if you write a story where sometime in it Batman picks up a machine gun and mows down the bad guys then he stops being Batman because Batman would never do such a thing. This would also remove all value from that tragic boyhood event of him witnessing his parents’ murder, rendering it meaningless because that traumatic event exists as the reason why he possesses the Key Components of never using guns, never killing, and is obsessed with fighting crime.
Richard Dean Anderson’s MacGuyver shares this same no-guns Key Component because as a kid he witnessed his friend accidentally shot while playing with a pistol and almost dying but for MacGuyver saving him through his more famous Key Component ingenuity of inventing things on the fly. This instilled the Key Component in MacGuyver that he never in any situation would ever use a gun because he absolutely deplores them.
In contrast to the previous examples is the Punisher a.k.a. Frank Castle who uses lots of guns and his Key Component is that he always kills. Once the Punisher sets his sights on a bad guy, consider them dead. The Punisher stops being the Punisher if you have him surrendering to compassion and leaving a pleading bad guy alive because you remove his Key Component which defines him as the Punisher. The mafia who murdered Frank Castle’s innocent wife and children and left Frank for dead showed no mercy or remorse . . . and for that neither does the Punisher his targets.
The Key Component of the protagonist of my fantasy Soothsayer Series, Banzu, is protecting innocent lives even at the cost of his own. Because of this I burdened him with the bloodlust curse which all Soothsayers are born with, but it remains dormant inside of them until the first time they kill awakens it. Then the bloodlust curse drives them to keep killing while causing madness so that they eventually become an indiscriminant slaughterer, which would obviously include lots of innocent people. This is in direct opposition to Banzu’s Key Component of protecting innocent lives even at the cost of his own, providing an interesting conflict of character.
Captain America a.k.a. Steve Rogers is a great example of someone with tons of Key Components (truth, freedom, justice, liberty, protecting innocents . . . et cetera) and we’re shown them throughout the entire run of MCU movies. He wants to join the military to protect the innocent people the Nazis are brutalizing despite being small and weak. He throws himself on the dummy grenade to protect his fellow soldiers during basic training even though they bully and make fun of him. He stands against S.H.I.E.L.D. when he discovers they want to police the world through pre-crime arrests and detention. He defends his best friend Bucky against Iron Man after Tony Stark learns Bucky a.k.a. the Winter Soldier murdered his parents because Bucky was brainwashed at the time and did not commit the murders of his own free will. When Vision offers to sacrifice himself because Thanos wants the Mind Stone in his forehead and will stop at nothing to get it, Captain America refuses him because, “We don’t trade lives.” When he and Tony argue about stopping Ultron as well the greater threat behind Loki’s attempt at enslaving the world through Chitauri invasion, Tony asks how they’re supposed to deal with that greater threat after excusing why he and Bruce Banner created the Ultron murderbot. Captain America simply says, “Together.” Tony rebuttals with, “We’ll lose.” And Captain America responds, “Then we’ll do that together, too.”
Growing up, us comic book nerds loved to argue about who would win in a fight between our various favorite superheroes. Over the years this resulted in what became known as The Batman Factor. Because, you see, Batman’s dominant Key Component that sets him apart from every other superhero in existence is that no matter how bad you beat him down if you leave him alive he will slink away into his batcave, discover some unique way of exploiting your greatest weakness, then come back with a vengeance, beat you to within an inch of your life and let you know that he can do it again any time he wants, then he’ll walk away while leaving you alive but forever broken. Because what defines Batman as Batman is that no matter who he’s up against, he always wins in the end. Above all, that is what makes him Batman. Remove this Key Component and you render him just a forgettable guy in a costume fighting crime. Provide this Key Component and you get one of the most beloved superheroes in all of comic fandom, recognized today by literally billions of people, who has endured for over eighty years of great storytelling.
The Key Component defines your protagonist by making them who they are, whether they possess one or several. It also helps you write your story because knowing their Key Component allows you to put them into situations that challenge it, where they can utilize it best, as well where it can be exploited against them. Discover your protagonist’s Key Component and you’re well on your way to making a great, memorable character.