Game Of Thrones: 7 Dumbest Mistakes Made By Characters (And What They Cost)

7. Ned Stark Admitting He Knew Cersei's Secret (But Not To Robert)

The Mistake: Ned admitting to Cersei Lannister that he knew her children were born of an incestuous relationship with Jaime.

What It Cost: His life (and incidentally the War of the Five Kings). Though Ned attempted to gain an upper hand over Cersei by threatening her with her secret, it not only prompted Cersei to destroy the letter proclaiming him as Protector of the Realm, but it also pressured her into plying Robert Baratheon with alcohol before the hunt that killed him.

If Ned had chosen to tell Robert instead, there's no way that Cersei would have lived (and there's a high chance that Joffrey and the rest of the children would have been killed, too).

Ned wouldn't have been executed and Westeros wouldn't have exploded into political chaos. That's a fairly big blunder,