Without reviewing hundreds of movies the Subway Fight in The Matrix is my choice.
Alternately, the fight in Seven Samurai where the sword master is introduced.
Animated? The fight between Motoko and the puppet terrorist stands out, as it emphasizes a lot of the themes of the story; Invisible, super strong, and super-capable, Motoko completely and effortlessly defeats the puppet terrorist despite his installed martial arts abilities. He simply cannot meaningfully fight her, and when the fight is over she looks on with something like alien pity.
Oh that fight when Algren groks his sword training in The Last Samurai and defeats like four guys in the dark is really cool.
Oh, the fight in Pirates of the Carribean where Jack manipulate's Legolas' academic but inexperienced fencing to get to the other side of the room in an attempt to leave without hurting him. it says so much about who the characters really are. You get an early hint that Jack is much smarter, more capable, and more aware than his goofy persona suggests, and also of his weird humanism; He's no one's enemy, he just wants to go his own way. Plus that line "People arent' cargo, mate" is a great encapsulation of humanist philosophy, and you can extend it to anti-capitalism if you want.