Friedrich Wilhelm I of Prussia.
The bad-tempered "Sergeant-King" wore his officer's uniform around the house and turned the royal gardens into a military grounds. He was known for fits of screaming rage, calling everyone in sight "blockhead", sometimes beating officials with a stick, and knocking out the teeth of several judged whose sentences displeased him.
At the age of eight-teen, Friedrich [his son] tried to run off to England to catch a glimpse of his intended English bride. When young Friedrich's scheme, planned by his best friend - and perhaps his lover- was foiled, the furious Friedrich Wilhelm decided to have his son executed. When dissuaded by his officials, Friedrich Wilhelm made the young prince watch from a prison cell the decapitation of his friend. (From A History of Modern Europe - John Merriman.) So yeah, he was pretty dickish. And his actions made his sensitive, music and literature loving son into a total "aggressive absolute monarch".
