Armor Is Useless: Massively subverted when Asta gets stabbed in his chest by Mars.
Collapsing Lair: After finally defeating the Hell Lotus magic knight, Mars, our heroes (Asta, Noelle, Luck, Yuno, Klaus and Mimosa) find that they have to escape the now quickly collapsing dungeon.
Curb-Stomp Battle: Mars, the mineral mage working with Lotus, inflicts this on Yuno and his teammates. Even after Yuno stops holding back, he's much worse for the wear, while Mars isn't even scratched.
Hoist by His Own Petard: Lotus can't see through his own smoke and has to rely on sensing his opponents' magical signatures. As a result, he's caught off guard since Asta, being an Un-Sorcerer, has no magical signature at all. His earlier advice to Luck about the value of teamwork also works against him since Luck takes the advice to heart and cooperated with his teammates to beat him, something Luck is quick to mention.
The Worf Effect: The members of Golden Dawn (Klaus, Mimosa and Yuno) suffer this at the hands of Mars, the mineral mage, from the Diamond Kingdom, despite being from the best magic knight group and Yuno's ace tendencies. This serves the purpose of demonstrating how freakishly powerful Mars was, and Asta would need more than standard determination and anti-magic to defeat him.