Habonk
A habonk is a person who thinks they’re tough, but they’re just clumsy and weak.
My uncle is a habonk. He tried to wrestle a bear and fell into a lake.
My friend is a habonk. He tripped over a chair and face-planted into a cake.
That guy at the park is a habonk. He tried to do a backflip and landed in a puddle.