kadoonka - A total idiot who thinks the sky is green and still manages

A total idiot who thinks the sky is green and still manages to mess up their own life.

My neighbor is a kadoonka. He tried to fix the sink and now the whole kitchen is flooded.

My math teacher is a kadoonka. She said 2 + 2 equals 5 and didn't even apologize.

My little brother is a kadoonka. He tried to ride a bike and fell into a puddle.