Devadatta
Devadatta was the maternal first cousin (or in some accounts paternal first cousin) of the Buddha. He was ordained into the sangha along with his brothers and friends and their barber, Upāli when the Buddha preached to the Shakyas in Kapilavastu.
For a time Devadatta was highly respected among the sangha. Shariputra is said to have sung the praises of Devadatta in Rajagaha. After some time Devadatta developed siddhis and his intention is said to have been corrupted. After gaining these siddhis, Devadatta attempted to kill the Buddha on several occasions, commonly thought to be motivated by jealousy of the Buddha's power. He is reported to have rolled a boulder toward the Buddha, piercing his flesh, and to have incited an elephant to charge at the Buddha.
Devadatta then attempted to split the sangha into two, with one faction led by himself and the other by the Buddha. However this attempt failed as all of his converts returned to the Buddha's sangha.
Devadatta was reputedly remorseful toward the Buddha late in life. He is reported to have walked to the monastery where the Buddha was staying to apologize to him but, as a result of bad karma, he was swallowed up into the earth and reborn in Avici.
Read more about this topic: Family Of Gautama Buddha