- Episode 1/Volume 1, Diablo has his first outing as an actual Demon Lord. Having No Selled an attack by a Salamander summoned by a racist Jerkass, Diablo proceeds to use an One-Hit Kill style Explosion on the summon that that Megumin would be proud of (and probably in awe of too).
- Diablo shrugs off the elf squads' arrows, especially a special holy arrow. He then unleashes a hellish winter to stop them.
- Edelgard gets a villainous one where before she invaded Faltra City, she had the foresight in sending in a sleeper agent to take out Celes. It could have worked if it weren't for those meddling girls and their OP Demon Lord, who once he heard about the sleeper agent, flat-out nuked the entire army with White Nova.
- Say what you want about Emile but it took a big pair to take on a very powerful Demon wizard that just decimated most of the Adventurers. And to his credit, he lasts long enough to allow Diablo to come back, who assures him that he was a hero today.
- Diablo finally gets a weapon that will help dampen his powers enough so that he won't kill his opponents. This means he can go all out whenever and wherever he wants.
- Rem knocking a cowardly bounty hunter to submission with a single punch, after appearing behind him out of nowhere.
- Emile doing a Big Damn Heroes and saving Shera, saving Diablos the trouble. He may be overblown, but his heart is definitely in the right place.
- Having recovered from his Heroic BSoD, Diablo heads straight to the Elf army's camp and wipes them all out. When he sees Shera in distress by her monster of a brother, his face shows he is not amused.
- The collars work out for the heroes' benefit. Diablo uses them to reveal Shera's true feelings, negating the spell Keera places on her to control her.
- Diablo defeating the Hydra. If it can regenerate any part of its limb, might as well roast everything.
- Diablo's fight with Galford. Unlike the last time where he defeats his opponents in a one sided battle, the Demon Lord from another world has to face someone who is nearly equal as him and Diablo has just been handicapped, severely tired from a recent fight. However, Diablo already made his resolve that he'll fight to protect those he cares for. Special mention goes to his magical mines that he set up to trick Galford. There's also him having the foresight to have a back up plan in case things goes wrong and fires his lighting strikes to defeat Galford to submission.
- Simple as it is, Diablo reflects Saddler's (temporary) petrification magic against him, who very much deserved it.
- After Rem sacrifices her life to protect Klem, the demon girl is deeply enraged at this and transforms into her One-Winged Angel form to avenge Rem's death. Klem made sure that Saddler suffers despair unlike any other and gives him an unceremonious death.
- Volume 9 has a few badass moments in it. First, Galford reveals that he has a trump card up his sleeve which he uses to kill Ryoka, a Fallen that had been giving him a hard time and killed/injured several adventurers with ease, next Krum and Edelgard show up at the right moment when Modinalaam is ready to finish everyone off and proceeds to completely Curb Stomp the Greater Demon Lord until he goes one-winged angel. When Diablo shows up and sees the result of the fight, he admits that if Krum fought him seriously in her child form, he would have lost the fight. Then Diablo, fresh off his training to become a magic swordsman, along with Rose and Sasala, a level 200 Swordmaster Dwarf (dog eared people), proceed to clean up after everyone with ease. Finally Rem gets one where she, after being possessed by Modinalaam, reveals that he's terrified of Elixirs, as Elixirs can cure all bad statuses, and Modinalaam is the "Demon Lord of Insanity" with insanity being a bad status.Diablo: No one playing the game would have tried this, Elixirs are hard to come by. Is it that simple?
Awesome / How NOT to Summon a Demon Lord