Of course Over Justice's Dark and Dark attack didn't work against Lalaco. It's freakingDark and Dark! It's still hot enough to burn Life Fibers, though... Poor guy.
While the scene of Trigger-Chan high-fiving Akko at the end is meant to be a teaser for Little Witch Academia (2017), since Space Patrol Luluco is intended to celebrate Trigger's 5th anniversary and Little Witch Academia (2013) is the studio's first major anime production (not counting Inferno Cop), the scene can also be seen as a heartwarming gesture towards one of the productions that started it all.
The world of Life Fibres that Luluco and friends visit is a terrifying callback to Kill La Kill - With a planet so encased in Life Fibres that it looks like a wool ball from orbit, it is clearly in the late stages of the Life Fibre's development, before the stage where they induce a controlled detonation of the planet in order to propagate throughout the universe. While Over Justice's flames are used to burn the life fibres before they can really spread, there's still a risk that some got away to attack other planets.
