>>281670164
What you describe was before isekai. Had you been living in a cave the last 15 years?
Ainz genocides an entire kingdom because one retarded noble attacked a carriage carrying grain.
Rou targets random unrelated strong heroes he has no grudges with just because he can take their powers by eating them.
Kumoko is willing to kill any amount of humans because some human leaders chose to double down on increasing the burden of a holy-maiden-like goddess figure that sacrifices herself for the whole world to function as it does.
Rimuru kills 20,000 human soldiers and denies them their afterlife by also devouring their souls, but lets their actual leaders go virtually scott-free after a few days of very painful and bizarre torture sessions. He also acts like an American Neocon who goes into proxy wars, instigates regime changes that result in puppet-governments fully in control of himself and creates a situation where most of the human nations have no choice but to always side with his decisions or face almost certain ruin.

What you talk about is probably the typical cliché scene where the heroic MC corners a mustache-twirling villain and the villain begs for his life and the MC lets him live but when the MC turns around the villain screams "gottcha!" and tries to kill the MC one more time, only to be stopped by the MC himself or a friend that comes to the rescue, with the villain being arrested and put into prison, or the villain just conveniently slips up while trying to attack the MC and conveniently stabs his head onto a sharpened ornamental weapon in the room for "haha, poetic justice!" without the MC having to dirty his own hands. There are still isekai like that but it's much rarer now than it was before isekai. Rather moral normalfag-friendly MCs being popular was one of the reasons isekai came to be as a sort of counter-culture in the first place.