The hallmark trait of a Karen is entitlement. Most Karen's wants to control every person around them, even if they is making the most demanding and absurd request. Not only do they believe the world revolves around them, but they are going to ensure that everyone around them knows they think the world revolves around them and make it the public's problem.
One of the worst breeds of Karen's are those who demand you inconvenience yourself for them and their spoiled rotten kids. They yell at restaurant and store staff because little Billy's eggs are touching his hash or they don't have the right American Girl Doll in stock for little Suzie. There are some Karen's so entitled that they go even further than this, making insane demands on random citizens going about there day acting normally. This was the case when one Redditor posted about their experience with an insanely rude mother living in their apartment building.