Chapter 72's ending. Both the original and the Retcon.
Original:Jasper brutally beats and then rapes his mother Cersei in blind fury after finding out about her incestuous relationship with Jaime.
Retcon: Jasper has his mother Cersei brutally punished by shaving her hair and pulling out her eyes.
The beginning of the Witch Hunt. Robb wakes up to the sound of screaming, rushes outside, and sees Jasper's men butchering Red Priests and their followers, with some even raping the women among them! He rushes to confront Jasper... and finds him surrounded by the corpses of several Red Priests he personally slew, covered in blood and grinning like a madman. When Robb gets over his shock and demands an explanation, Jasper bluntly states that he ordered his men to wipe out the worshipers of R'hllor "completely and utterly." Robb tries to condemn the acts of rape and torture, to which Jasper responds by delivering a chilling Hannibal Lecture about the reality of war—though he ultimately confirms that he did not explicitly order his men to rape the women. Robb asks if this means he will be targeted since he follows the Old Gods, to which Jasper jovially assures him that that won't happen. When a large group of Red Priests try to surrender, Jasper, ignoring Robb's pleading, has his archers slaughter them.
Jasper's threat to the Dornish:
"Aegon the Conqueror and Daeron the Young Dragon tried to occupy Dorne. If you refuse to obey me, I shall eradicate it. If you object to my laws on your principality, I shall send in my army that already occupies half your country. Your men may flee to the mountains as they did in ages past, but I shall kill their families, burn their villages, salt their fields and poison their wells. Then I shall tear down your castles and holdfasts and take their wealth and treasure for the crown. I shall ride a thousand horses over it till none remember that a castle ever stood there. Then I shall send in some of the many displaced peoples from across Westeros, as well as a man of proven loyalty, to raise a new castle and resettle the land - men, women and children who have no difficulty obeying my laws. Your armies have been destroyed in this war and the last one. Your ability to resist is at its last thread. Do not make me cut it."
One of the Dornish lords thinks he's bluffing. Jasper has him clapped in irons and forces him to watch as he proves that he isn't. The results of the massacre, called the Ruination of the Hellholt, are revealed in gruesome detail in the sequel. Here's the link.