Actually, its Nehru that is the more immediate to blame, since he seduced Mountbatton's wife-- the enraged Mountbatton then ordered that the partition would occur over a period of 30 days, which accelerated the violence.

As far as Gandhi, it is very difficult to look at his career and not see a man reflecting the interests of his class. His first hunger strike was against the Untouchables, ensuring that large party would have to subsume its interests into that of a larger political party which eliminated the Untouchables as a threat.

As far as the direct answer to the question, the partition was the separation of India and Pakistan; and Gandhi receives much of the blame for encouraging that partition. He wanted there to be no violence and thought separating Moslems and Hindus (to the advantage of the Hindus, which Gandhi was) would lead to less violence. He failed to understand that all of the Moslms were Indian; he treated them as people who needed to be separated from the Indians. However, virtually all Moslems were Indians who had converted to Islam from Hinduism--huge numbers of Moslems were former untouchables--becoming a Moslem meant you had to pay the tax, but you were allowed to be part of a larger society-- you didn't have to hide away from Hindus who would be soiled by merely making eye contact with you. Becoming a Moslem was a huge social step up for untouchables, but Gandhi spent his time pretending that Moslems were 'alien" and non-Indian. Because that was the interests of his class and religion. In sum, Gandhi gets blame because he represented the interests of his people at the expense of Moslems.