Dragonrend

Spoiler Alert
The Dragonrend shout was originally used to defeat Alduin during the Dragon war. The shout was used to force Alduin to land so the War could be ended. When Alduin landed an Elder Scroll was used to defeat Alduin, this didn't work as Alduin was only sent to another time.

Shout
JOOR, ZAH and FRUL are the necessary words of power needed to use this shout. They are easy to gain as they are all earned during the quest Alduin's Bane.