Xanxus

Xanxus (ザンザス, Zanzasu?) is one of the main antagonists in the manga and anime Katekyo Hitman Reborn as well as the leader of Varia, a group of assassins, under the control of the Vongola family.

He entered the family at a young age through his mentally-ill mother finding out about his Flame of Wrath, taking the boy to Vongola Nono, the current leader of the family, thus taking the child as his own. Xanxus finding out years later that his adoptive father only took him in through pity, enraging the teenager to the point where he founded his own Guardians to plan a rebellion considering Timoteo had no intention of handing the title of "Vongola Decimo" to him because he did not posses "Vongola Blood".

Power and Abilities
Xanxus is the second person to obtain the "Flame of Wrath"  (憤怒の炎, Fundo no Honō) which Vongola Secondo was thought to be the only person able to posses this power. It is a very destructive and powerful flame, known as the strongest flame among the Vongola Bosses, it appeared whenever Vongola Secondo became enraged.