The Gosei Great Gattai sequence in Epic 2. What pushed the scene most is NoB singing its Leitmotif in the background.
The Goseigers defeating D'reptor in Epic 12, first each tribe gives him a good beating, followed by Gosei Buster's Gosei Dynamic finisher. And to top it off, they combine Gosei Great, the Seaick, Landick, and Skick Brothers, and Datas Hyper to form Hyper Gosei Great taking him down.
Their final battle against Mons Drake in Epic 15 when they blast Mons Drake into his ship.
Alata and D'reptor's final battle in Epic 16.
Epic 17; pretty much the latter part with Gosei Knight and Groundion's debut.
Epic 19 takes it further with the premiere appearance of Gosei Ground.
The debut of the Super Goseigers in Epic 24 definitely counts.
Two Words: Gosei Ultimate
Epic 47 - Hyde vs Burajira.
Epic 48's whole-episode long battle between Alata and Dark GoseiKnight
As expected with most teamup movies, Goseiger vs Shinkenger is a wealth of awesome moments. Super Change cards for all the Shinkengers, Ground Hyper Gosei Great, and nicely done henshin and role call sequence to boot, never mind the Gokaiger'sEarly-Bird Cameo.
Epic 50: Alata, the Red that tends to get picked on for not being Rated M for Manly like the ones before him, kills Burajira, the Big Bad.