Ozan:

Imagine that you see a train running towards five people tied up on the tracks. You can’t stop the train. The only way to prevent the train from running over the people is to pull a lever and make the train turn. However, on the turn, there is one man tied up. Do you choose to divert the train or not?

This is a common thought experiment in philosophy. If you take a numerical approach, you’d say you’d rather have one person die than five. However, many people actually choose to allow five people to die, because allowing people to die is not the same as killing someone. And this is in fact a distinction that is often made in criminal law. But regardless of which choice you make, we can all agree that it’s between something that is less wrong and something that is more wrong. It’s not right to let someone die, and it’s not right to kill one person over five—it might just be less wrong.

Even beyond ethics, “couldn’t be more wrong” is a common way to express emphatically that someone is wrong.