I had a slightly different take on the final scene, and I’m a little surprised that nobody else had the same take. Must be just me then.
Yes, Andrew starts playing out of spite, because he’ll show Fletcher what he’s made of, and he’s happy to disrupt Fletcher’s show while doing it. But as Andrew goes No More Mr Nice Guy, and he starts yelling obscenities and crashing the cymbal in Fletcher’s face, a change really does come over him. And the looks they exchange in the final cut are looks of mutual recognition.
Sure, it’s recognition that Andrew is now as much a musician as a Fletcher is. But it’s more than that.
It’s recognition that Andrew is now as much a monster as Fletcher is.