I would put this in TOP 5: Episode 9’s “The Scoop!” Ghastly and keeps you on the edge.
This is easily has one of the best battles, and I don’t even like Rayquaza. I never met Deoxys in-game either, but recognized that BGM theme once it began, and had a pretty good feeling of its identity before it folded out from its compressed form. The Scoop is both ghastly, and beautifully blends well as two pokemon are encompassed in space. Outer space that is. Also, Deoxys actually puts up a challenging fight, having a speed, defense and attack mode.