A psycho is a person who has a mental illness and acts in a very strange or dangerous way.
The word psycho can make people think of fear or danger.
Examples:
The psycho scared everyone at the party.
I don't want to be near the psycho.
The psycho in the movie was very scary.
The psycho tried to scare us with a funny mask.
The psycho in the story could do magic.
The psycho in the story was very, very scary.