Garrosh Hellscream

As the renewed Alliance-Horde war developed, Garrosh's thirst for power corrupted him to the point that he did not care about the means used to bring the orcish supremacy on Azeroth, with himself as the world's supreme ruler - going as far as to unleash the full power of the dead Old God's heart by resurrecting it using the Pools of Power, effectively destroying half of the sacred pandaren Vale of Eternal Blossoms.