Hades is the leader of the Grimoire Heart Dark Guild, whose goal is to unseal Zeref. He seems to be calm and confident man who shows no signs of fear to his enemies, especially Makarov. He was described by Makarov as a "great Master who taught harmony and led the Guild to the proper path."
Hades, known as Precht back then, became the second Master of Fairy Tail after Mavis Vermilion. Some time later, in the Year X736, Precht appointed Makarov (40 years old at that time) as the third Master and his successor, much to the man's dismay. Ignoring Makarov's claims that he wasn't fit for it, he praised Makarov's love for his allies and his capability to believe, claiming that he would have made Fairy Tail into a good Guild. He then left on a journey.
On such journey, he traced the roots of Magic back to Zeref, where he saw "what can be called the Essence of Magic." It is presumably around this point that he reformed his ways and became a Dark Mage, and then founded Grimoire Heart.
So we have a bunch of powerful mages, villains and dragons who encompass the thrilling Fairy Tail universe. But which of them are truly the strongest Fairy Tail characters of the lot. It's time to step inside the battle field, and settle the score once and for all!