The Dark knight Sparda

Direct text from Devil may cry wiki:
Sparda was once one of Mundus' Devil Knights, and apparently took part in the invasion of the human world. At some point however, he suffered a change of heart and switched sides, fighting to protect the humans. He defeated Mundus' demon armies, before moving onto the Prince Of Darkness himself. Sparda defeated Mundus, and sent him and his armies back to the demon realm. In order to close the gateway, Sparda used his own blood, along with the blood of a human priestess, in conjunction with his sword and a mystical amulet. Pouring his demonic energy into the sword allowed him to close the door between realms, however this also robbed him of the lion's share of his abilities. Sparda could still access his powers when he used the amulet but only for a brief time. Sparda's activities over the next two thousand years are shrouded in legend, however it is understood that for a time, directly after defeating Mundus, he ruled over the humans before eventually vanishing. Devil May Cry 4 raises an interesting plot element, as it would seem that Sparda sacrificed his powers only to seal off the full functions of the Temen-ni-gru, as according to the Order of the Sword and by Dante's admission, Sparda sealed the true hell gate by using Yamato. He showed up again in the twentieth century where he met and fell in love with a human woman named Eva. He fathered the twins and for a brief time lived with his family, before he again disappeared. Many believe he died, although in DMC2 Dante hints he may have passed into another realm