We have talked and debatted endlessly about the incredibly crazy and stupid actions and decisions taken by Cersei and Joffrey, as queen regent and king respectively, which would have astonished even the worst Targaryen kings save perhaps for Aerys II at his maddest.

But what about the other members of their family, the Lannister family ? What are the most crazy if not outright most stupid actions and decisions taken by other Lannisters such as Tywin, Tyrion, Jaime and others ?

For Jaime I'd guess that acting so smug to and trying to bully and bribe a gang of sadistic and lawless madmen such as the Bloody Mummers with a condescending tone, and despite realizing that the Mummers are very dangerous and don't respect or fear him and his name, with one of them hitting him, take the cake. He was basically asking for Vargo Hoat to maim or kill him with this attitude.

For Tyrion I would say that it is not even trying to go after Littlefinger, to actually investigate and try to get rid of him, despite knowing too well that Littlefinger framed him for the dagger and attempt on Bran Stark's life and being totally treacherous.