Whenever something, usually dangerous or outright deadly, happens to a character, but they're surprised by how easily they can handle it.
Examples:
Limbus Company x Arknights Collab "Pilgrimage of Compassion": The Sinners get caught off-guard and most of them are shanked with poisoned knives. The Arknights characters are horrified, and Amiya in particular tells Dante that the poison is designed to make them into Sea Terrors. She's remorseful as she tells them that the only thing they can do is kill them before they transform... to which Dante responds with "That's... not so bad?", and tells the resident Sea Terror hunter Skadi to go ahead and kill them as painlessly as she can, which Skadi obliges. Everyone else is extra horrified that Dante is that quick to have their friends killed off... and then Clockhead just does his usual rewinding and they rise back up, good as new. They even get to aurafarm a bit, as seen in the CG.
Frieren: Beyond Journey's End: In Chapter 5, Fern and Frieren travel to find where the powerful demon Qual is sealed in order to kill him. This Qual is legendary, having developed and perfected a spell that could kill anything it hits, a one-shot kill. When unsealed, he talks a bit with Frieren, and then releases a massive ray called Zoltraak... which is easily blocked by a basic defense spell from Fern. The young mage is confused why, after all that build-up of how dangerous Qual is, his masterpiece is the basic attack spell every mage can do. Frieren then reveals that the spell really did live up to the hype... 80 years ago, that is. In that time, humanity's mages have managed to absolutely dissect the spell, to the point it's the most basic attack spell learned by mages, and its counters are equally as well-developed, be that equipment or the basic defensive spell.