9. Gregor “The Mountain” Clegan
Gregor Clegane, better known as The Mountain, is a freakishly huge man who stands close to eight feet tall. As the head of his house and a bannerman for the Lannisters, Clegane does the bidding of Tywin Lannister without question.
As a child, Gregor burned his brother Sandor’s face in a brazier because his Sandor, later known as the Hound, played with one of Gregor’s toys. A few years later, when Clegane was 17, he participated in the sack of King’s Landing at the end of Robert’s Rebellion. As one of the few men to infiltrate the Red Keep, Clegane murdered the Targaryen children and sexually assaulted Queen Elia Martell, Rhaegar Targaryen’s wife.
Clegane is very active during the War of the Five Kings. He routinely pillages the Riverlands, tortures prisoners and murders innocent civilians. His reign of terror is likely not over after his duel with Oberyn Martell. Although he was poisoned and seemingly died, another knight named Robert Strong who just so happens to be eight feet tall shows up with Qyburn in A Dance with Dragons. Since the show resurrected the Mountain, it’s a good bet that Robert Strong will have a similar arc in the remaining books.
8. Walder Frey
Right off the bat, it’s pretty clear that Walder Frey is a slimy individual. At the beginning of the story, he is 90 years old and had been the overlord of the Twins for decades. He is also betrothed to his eighth wife and has over one hundred direct descendants. The sheer amount of Freys makes his house formidable, but Walder is content to let them all scratch and claw at each other to gain his favor.
We also learn that Walder is notoriously late to provide help during wartime, as he prefers to wait until he knows which side will win instead of holding to his oaths. This comes into play when the War of the Five Kings breaks out and the northern army needs to use Walder’s bridge to cross into the south. The Frey army is guarding the Twins and Walder doesn’t let the Stark forces pass until they agree to several marriage contracts and other concessions. The most important part of the deal is that Robb Stark must marry one of Walder’s daughters.
However, Robb betrays this pact in A Storm of Swords when he marries Jeyne Westerling instead of a Frey girl. This proves to be a fatal mistake, as this betrayal motivates Walder Frey to form a secret pact with Tywin Lannister and Roose Bolton. Walder hosts Edmure Tully’s wedding at the Twins, but then his forces kill or capture the Northern soldiers in what becomes known as the Red Wedding.
Robb Stark and his mother Catelyn are the most notable casualties of the feast, and Walder was content to murder them and help supplant the Starks as the Lords of the North because Robb broke a marriage pact. Talk about a fragile ego.