Vergil is my personal favorite, that's why I mention him last.
Vergil is Dante's elder identical twin brother, though the two are near-polar opposites; unlike Dante, Vergil embraces his demonic heritage. He is a chief antagonist in Devil May Cry 3 as well as a playable character in the game's Special Edition. After he is betrayed by Arkham at the end of the game's second act (the end of mission 13), he temporarily teams up with Dante near the end, before reverting to his villain role. Throughout the game, Vergil seeks to undo the seal of Sparda hidden within the Demonic Domain, and claim the entirety of their father's power for his own, regardless of the effects this will have on the human world. To do so he needed Dante's half of their mother's amulet, so he lured his brother out with the intent of taking it by force. His dialogue at the end of mission 8 indicates that he seeks this power to compensate for being unable to save their mother . Vergil battles Dante three times in the Devil May Cry 3 storyline. Their first battle is on the highest level of Temen-Ni-Gru, where Dante is soundly defeated by Vergil, who then takes Dante's amulet. Their second battle is at the bottom of the tower, where the twins battle to a draw before their battle is interrupted. Their final battle is near the entrance to the demon realm, where Vergil is finally defeated. While Dante escapes back to the human world, Vergil chooses to stay behind. Should the player be able to defeat at least 100 demons before the credits finish, the player is shown a cutscene with Vergil rising to his feet in a lake of blood, and looking into the sky to see three large glowing orbs in the sky – Mundus as he first appeared in Devil May Cry. Vergil decides that if his father was able to defeat Mundus he can too, and then charges at the orbs with his sword ready. Vergil survives his encounter with Mundus, but becomes enslaved and apparently brainwashed. In the first game, he appears as a demonic dark knight, called Nelo Angelo (a mistranslation of Nero Angelo). Dante encounters Nelo Angelo three times in Devil May Cry, and each time Nelo Angelo sees Dante's half of the amulet, he flees the battle. In their final encounter, Nelo Angelo uncovers his face to reveal that he is Vergil. In the end Nelo Angelo appears to explode, leaving his half of the amulet behind.