The Frieze arc escalating, especially from Krillin's death onwards. Goku turning SSJ, the entire battle sequence, the planet rapidly getting destroyed, Goku initially sparing Frieza who then is a dick for the final time, the planet exploding as Goku tries to desperately save himself... I don't think anything was that epic before or after that sequence to be honest, especially considering death seemed to still have some sort of consequence (despite the Dragon Balls' power), and certain decisions and situations seemed rather final. Of course, that wasn't the case later, but if you didn't know where Dragon Ball Z was headed after that and was deeply invested in the story and lore, what happened on Namek has been absolutely epic and devastating.
