10. Robb Executing Karstark
It's hard to fault Robb for this one. Lord Rickard Karstark had, in fact, committed treason by murdering Martyn and Willem Lannister, whom Robb was keeping prisoner in Riverrun as leverage to potentially retrieve his sisters from King's Landing. Of course, Jaime Lannister had murdered Karstark's son Torrhel during his escape attempt from Robb's army's camp. When Jaime was recaptured, Karstark demanded that Jaime be executed as justice for the death of his son. Catelyn manages to convince Karstark to respect his king's decision to spare Jaime's life with the promise that he would be punished. Karstark is robbed of his chance for retribution when Catelyn releases Jaime in Brienne's custody to return him to King's Landing in exchange for her daughters. Robb's decision to execute Karstark is understandable given his continued insubordination and that pesky honor his father instilled in him. Unfortunately, Karstark was Robb's most influential bannerman and just as his wife, mother, and military advisors predicted, House Karstark's soldiers withdraw from Robb's army, leaving him in dire straits. With not enough men to continue his war effort, Robb has no choice but to seek reinforcements from Walder Frey. And we all know how that turned out...