These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Crowning Moment of Awesome: the final battle of the first series, which involves Godzilla-sized energy clones beating the everloving crap out of each other... while over a densely crowded capital city.
Drunk Lanfeust abuses his newfound power to create a dragon out of thin air. The dragon is too fat to fly... and instantly goes splat on the ground, giving the resident Fortune Tellerseveral years' worth of reading material.
Thanos learns where Lanfeust and Co. are. He interrupts a party in his honor, declares that his enemies will be dead soon and teleports to the reported location... only to come back a few seconds later asking for clothes, lots of clothes. Nobody told him Lanfeust had gone into the polar regions.
Nightmare Fuel: The death scenes are a lot grittier and more graphic than the art style would initially lead you to believe. Thanos's brother's death is especially creepy.
Seasonal Rot: Lanfeust Des Étoiles is generally viewed as much weaker than the original series. People complained about the very chaotic plot and that it was a vehicle for a hurricane of very oafish puns. Especially the puns.
Theiss Titillation Theory: Cixi, again. At one point she shows up in what is essentially a bikini, cut into strips, and those strips arranged in spirals for maximum effect.