Beach Episode: Subverted; the first chapter of the Underwater Temple Arc has the Black Bulls fooling around on a beach, with all the hijinks and fanservice required. Yami then tells them to quit screwing around, as they're on a mission, and they quickly get going.
Big Damn Heroes: Just before Vetto attempts his Last Breath Bullet, Yami saunters in after cutting through the prison he was left in. After congratulating everyone for their hard work (and secretly musing about how their effort inspired him) he invents a new spell and subsequently one-shots their foe with it).
Deus Exit Machina: Invoked when the Black Bulls attempt the Ocean Palace temple. The Water Priest excludes Yami from his challenges, and flat out tells him he's too powerful for this stage, and if he competes then the challenges won't be any fun. That said, it's subverted when the Eye of the Midnight Sun interrupts, elevates the threat level, and he's allowed to intervene.
Reality Ensues: During Asta's battle with Vetto in the Underwater Temple Arc, Vetto curb stomps Asta whilst listing the logical reasons why Asta hasn't a hope in the world of defeating him, those reasons being his poor attack range, general disadvantage against those who can magically enhance their physical ability, and his refusal to concede even when completely outmatched.
Villainous Breakdown: While not the most stable individual in the first place, Vetto really starts to lose it as the heroes stubbornly refuse to give up hope no matter what he does to them. In the end, he collapses into total despair when facing imminent defeat.