We never meet Front-de-Boeuf's father in person (thank goodness, because he sounds terrifying), but we do know that he is cut from the same cloth as his bullying son, so he must be an awful person. He is guilty of some truly horrifying crimes. Front-de-Boeuf, Sr. slaughters Cedric's family friend Torquil Wolfganger and his seven sons just so he can take possession of the castle at Torquilstone. He also kidnaps Torquil's daughter Ulrica and keeps her for many years as a sex slave.
There is some poetic justice in the fact that Ulrica uses her physical closeness to Front-de-Boeuf, Sr. to encourage the bad blood between father and son. They start to fight with each other as a result of her influence. When Front-de-Boeuf kills his father in a fit of rage, Ulrica gets some measure of revenge for the slaughter of her family and her own situation.
Front-de-Boeuf, Sr.'s cruelty is our clearest example of the viciousness of the earlier generations of Norman invaders. No wonder Saxons like Cedric are having trouble forgiving the Normans.