This is the fifth entry in a series about writing fight scenes from the perspective of a fight director. Note: I’m trying to work down from very high level concerns—stakes and consequences—toward lower-level details—individual fight moves and language. This week’s topic cuts across levels.
Imagine a duel between two identical fighters, equipped with the same weapons, trained in the same style with the same level of skill. Heck, you don’t have to imagine. This is a trap the early entries of the Marvel Cinematic Universe fell into.  Iron Man fights another guy in an Iron Man suit. Thor fights another Asgardian. Captain America fights another guy juiced on Super Soldier Serum. Ant Man fights another bug guy in a shrinking suit. These fights are dull. 
The best fight in the MCU, by far, is the airport brawl in Captain America: Civil War. And a big part of that is the asymmetry. Different heroes with different abilities fighting against each other, forced to resort to creative tactics because they can’t just go toe-to-toe and slug it out.
Asymmetry is one of the best tools for creating an interesting fight story. Let’s look at some possibilities:
Different weapons—I gave an example of this last week with the Paris fight in the tomb at the end of Romeo and Juliet, but an even better example is the final fight in Rob Roy between Rob, armed with a Scottish broadsword, and the dangerous fop Archie Cunningham, wielding a rapier. This is one of the finest sword fights on film.
In both these fights other more interesting symmetries are broken as well. The breaking of weapon symmetry creates interesting possibilities for choreography and visual excitement, but are secondary to the way they reinforce the distinctions between the characters. 
Rob Roy, for example, is simple, honest and direct. He only fights when he has too and only for what he believes in. Archie is a sophisticated but arrogant scoundrel who fights for sport. Their weapon choices and fighting styles reflect this. Rob comes at Archie head-on, with ponderous strikes that are easily side-stepped. Archie, with his nimbler weapon and fancy footwork, dances around Rob, toying with him, inflicting multiple wounds rather than finishing him off immediately.
And when Romeo attacks Paris empty-handed , that demonstrates Romeo’s desperation, but also reinforces his impetuous nature that has driven his actions throughout the play. It also shows the contrast between Paris, who expects Romeo to play by the rules and go peacefully, and Romeo, who’s never met a rule he didn’t break.
Different skillsets—Probably the best scene in the Daniel Craig reboot of Casino Royale is the free-running chase in the beginning. What makes it work is the filmmakers’ decision not to succumb to the action-movie pitfall of gifting the hero with whatever capabilities they need in the moment. Instead, they use the chase to reveal character. Every time the free-runner pulls off some feat of athletic prowess, Bond has to find another solution simply to keep up, demonstrating his resourcefulness, determination and, ultimately, ruthlessness.
Different ability levels—This is one of the classic techniques for making your protagonist the underdog. There’s a fantastic fight in Macbeth where the English army marches on Macbeth’s castle in overwhelming numbers, yet somehow one young English soldier  gets separated from the main force and confronts Macbeth alone. The fight is brutally short and one-sided, with Macbeth mocking the boy’s fear before slaughtering him.
A more upbeat example is the first Rocky movie, where Rocky is so outmatched he’s not even trying to win, he just wants to “go the distance” (which also gives him a different objective; ostensibly he’s trying to win, but he gains a moral victory just for surviving to the final bell).
Different objectives—If two people are fighting to the death, then their objective is the same—kill the other guy. A great recent example of a fight that breaks this symmetry is from Captain America: The Winter Soldier. Cap is fighting the Winter Soldier, who happens to be his best friend, Bucky but memory-wiped and brain-washed into an implacable assassin. The Winter Soldier wants to kill Cap, but Cap wants to save his friend. It’s a fight to the death which Cap can’t win. If he kills the Winter Soldier, he kills his friend Bucky. If he holds back, he’ll be killed. (This also gives them different rules of engagement).
Different rules of engagement—This is a staple of police dramas where the cops have to play by the rules while the criminals are free to respond with lethal force, but an outstanding example from science fiction is Ender’s Game, where (***spoiler alert***) Ender learns that the enemy in the interplanetary war that has devastated humanity is a hive-mind that assumed the people it had killed were brainless drones, therefore fair game. Unfortunately, he learns this after he has killed the Hive Queen.
I’m just scratching the surface here with possibilities for breaking symmetry. The idea I’d like to leave you with is that this can work at every level of abstraction of your fight—from the high-level story all the way down to individual fight moves—but that it’s most effective when the broken symmetry reinforces itself at every level.
1. There’s an obvious appeal to this from a storytelling point of view. The origin of the villain is tied to the origin of the superhero, so the audience only has to buy into one improbable thing at at time. Asgard exists! Super Soldier Serum is a thing! Plus the hero becomes personally responsible for the villain. Obadiah Stain wouldn’t have access to the arc reactor without Tony, Loki’s only interested in Earth because Thor eclipses him for the throne of Asgard, etc.
2. Okay, the Ant-Man/Yellowjacket fight was pretty fun, but mostly for the incongruities of scale. Beyond that it was mostly two guys punching each other.
3. For the converse, see any gladiator movie ever, where the weapons are changed up just for visual interest.
4. This is my choreography for a particular interpretation of the play and is not indicated in the script. But then, nothing is indicated in the script beyond dialog.
5. The character’s name is literally Young Siward.