In “One of These Days,” the local mayor shows up at the house of dentist Aurelio Escovar one morning with a painful toothache. At first, the dentist refuses to see him. The mayor is, apparently, not a friend, to say the least. Escovar has no desire to treat him. Yet the mayor refuses to leave and tells Escovar's child that if Escovar won't help him, he will come into the office and shoot the dentist. Escovar allows him to come in, as he himself fingers the gun in his drawer.
The dentist can see that the mayor truly is in pain and probably hasn't slept much for several nights. He agrees to remove the tooth, but he will do the job without anesthesia, and he takes his time about it. As Escovar prepares to pull the tooth, he remarks “with a bitter tenderness,” “Now you'll pay for our twenty dead men.” The mayor handles the pain well even though it must be excruciating.
From Escovar's comment, we can infer that the mayor is quite a corrupt man. He must be responsible, directly or indirectly, for the death of many people. We can also infer that the mayor and Escovar are on opposite sides of whatever conflict is going on. Escovar says “our” men, meaning that they are part of his group but not part of the mayor's. Pulling the mayor's tooth has given Escovar a small satisfaction of revenge at the very least.
The last bit of the story shows again that the mayor is a powerful person, probably powerful enough that the extraction of the tooth is the only chance Escovar will have at revenge. The dentist asks whether he should send the bill to the mayor or the town. The mayor remarks that it is all the same, revealing that he is indeed in control and probably uses his power to intimidate and even kill others.