The icchantika is, according to some Mahayana Buddhist scriptures, the most base and spiritually deluded of all types of being. The term implies being given over to total hedonism and greed. In the Tathagatagarbha sutras, some of which pay particular attention to the icchantikas, the term is frequently used of those persons who do not believe in the Buddha, his eternal Selfhood and his Dharma (Truth) or in karma; who seriously transgress against the Buddhist moral codes and vinaya; and who speak disparagingly and dismissively of the reality of the immortal Buddha-nature (Buddha-dhatu) or (essentially the same thing) the Tathagatagarbha present within all beings (including icchantikas themselves, though it is more hidden from their consciousness than in other individuals due to the massive accretions of sinfulness and delusion which conceal it from their sight).
The two shortest versions of the Mahayana Mahaparinirvana Sutra - one translated by Fa-xian, and the other a middle-length Tibetan version of the sutra - indicate that the icchantika has so totally severed all his/her roots of goodness that he/she can never attain Liberation and Nirvana. The full-length Dharmakshema version of the Mahayana Mahaparinirvana Sutra, in contrast, insists that even the icchantika can eventually find release into Nirvana, since no phenomenon is fixed (including this type of allegedly deluded person) and that change for the better and best is always a possibility. Other scriptures (such as the Lankavatara Sutra) indicate that the icchantikas will be saved through the liberational power of the Buddha - who, it is claimed, will never abandon any being.
Acchantika and Atyantika
Besides Icchantika, according to some Mahayana Buddhist scriptures there are Acchantika (阿闡底迦) and Atyantika (阿顛底迦). Acchantika are bodhisattvas refuse to attain nirvana yet. Atyantika are sendiment beings lack the characteristics of nirvana and would never attain nirvana.
The Mahayana Mahaparinirvana Sutra (Nirvana Publications, London 1999-2000), 12 Volumes, tr. by Kosho Yamamoto, editor Dr. Tony Page.