1- Rand's Revelation

This was pretty much the end of the Shadow's primary objective for the entire series. From Dragonmount to Dragonmount, Ishamael has been trying to convert Rand to his perspective. And he almost succeeded, but in the end almost is not enough. Ishamael lost, and there's no going back to that stratagem now.

2- Cleansing of Saidin

Overcoming Shai'tan's direct counterstroke. This was so important that Ishamael was actually willing to waive his rule about not killing Rand if it could prevent the Cleansing.

3- The Confrontation at the Eye of the World

Not sure about this one. The first two were easy, but this one... it set the Dragon Reborn on his path, broke Shai'tan's grasp on the seasons, forced the Blight to retreat and saved the Borderlands from an invasion. Sounds good, but many of these are replicated - the Battle of Falme and the seizing of Callandor both confirmed the Dragon Reborn, the Bowl of Winds broke Shai'tan's hold over the seasons, and Perrin saved the Two Rivers from invasion. This one's the only one that combines them all though.