Benedict Wigglestein ("Grandfather") Uno, Sr. is the main antagonist of the original animated televison film Codename: Kids Next Door: Operation: Z.E.R.O..
He is a demonic being who ruled the world before being overthrown by his son Monty Uno aka Numbuh 0. Many years later, he is revived by his other son and successor Father and begins transforming the people of the world into Senior Citizombies.
Grandfather is very tall and lanky, and significantly taller than a normal person. He has a bald head and a large beard with long, scraggly strands of hair.
Despite making only one appearance, Grandfather is the most powerful villain in the series.