Most of these come from romances rather than official history, please quote as appropriate.

1. Cao Cao was in trouble and stayed at Lu Boshe's house. Lu Boxe's family was ordered by Lu Boxe to kill a pig for entertainment. Cao Cao mistakenly thought that the pig-killer was plotting to kill him, so he suddenly went crazy and killed Lu Boshe's entire family. Later, when the pigs were tied up, they realized it was a misunderstanding. While escaping, Cao Cao met Lu Boxe who had gone out to buy wine. Cao Cao was afraid that Lu Boxe would go home and find that his family had been killed, so he went to the government to report it and killed Lu Boxe. This time it was not a misunderstanding but intentional murder. Cao Cao said a famous saying at this time: "I would rather betray the world than let the world betray me."

2. There was insufficient food and grass during the campaign. If the food was supplied normally, There will not be enough, but withholding supplies will lead to military morale mutiny. Cao Cao instructed the grain official Wang Jie to deduct grain and grass wantonly, and the rice grain sent out was less than half of the normal amount. After a few days like this, the morale of the army was on the verge of mutiny, and Cao Cao suddenly announced that the grain officer Wang Jie had secretly withheld military rations and should be executed for his crime. So Wang Ji was killed, and the morale of the army stabilized. Naturally, no one was responsible for the saved food and grass. Moreover, everyone thought that Cao Cao was a good man who made decisions for the soldiers, and he gained a high reputation among the soldiers.

3. Cao Cao has always been worried about being assassinated, so he deliberately pretended to be asleep and kicked off the quilt in the middle of the night. When the guard went to cover himself with the quilt, he suddenly drew his sword and killed him, and then went back to sleep. When he woke up the next morning, he pretended not to know and asked who dared to kill his own bodyguard. Others said that Cao Cao killed him himself. Cao Cao said, "It turns out that I like killing people in my sleep. This is actually true." From then on, no one dared to approach Cao Cao when he was sleeping, and Cao Cao himself felt relieved.

4. After Cao Cao killed countless people in his life, he "deeply regretted it and ordered him to be buried well and support his family." Those who were killed include loyal officials of the Han Dynasty who were not too cold towards Cao Cao like Liu Fu, and new heroes like Xu You who were overwhelmed with success, etc. Whenever Cao Cao found someone who must be killed, he would probably do this once. The effect is nothing more than killing the person you want to kill, and pretending that this behavior was just a moment of anger, and that you have regretted and made amends, thus preventing other people from dying and mourning, and collectively rising up to rebel against Cao Cao.

There are many others. I won’t go into details here.