Bill Gates created and ran Microsoft which was able to overcharge for its PC operating systems and Microsoft office product for decades because they held a virtual monopoly.
This extra money was taken from purchasers of personal computers for 30 years. Mostly the middle and upper middle class and wealthy.
Gates took $62 billion of his wealth and his so far used $27 billion of it to accelerate the curing of Malaria, other diseases, and bringing clean water, sanitation and better agriculture to the poor. He has also helped accelerate the curing of AIDS. Some countries which had negative GDP growth and big drops in life expectancy because of Aids have had their public health and economies turned around.
Bill Gates talked the other billionaires into giving instead of robbing them like Robin Hood
As of July 2013, 113 billionaire individuals and couples and one family group have signed the pledge to give at least half of their wealth to charity.
An estimate of the contribution promised by the first 40 donors, based on their aggregate wealth as at August 2010, was at least $125 billion.
Bill Gates convinced Warren Buffet to give most of Buffets billions to his Bill and Melinda Gates foundation.
Oxfam is an international confederation of 17 organizations working in approximately 90 countries worldwide to find solutions to poverty and related injustice around the world. Oxfam was originally founded in Oxford, in 1942 as the Oxford Committee for Famine Relief by a group of Quakers, social activists, and Oxford academics; this is now Oxfam Great Britain, still based in Oxford, Oxfordshire. It was one of several local committees formed in support of the National Famine Relief Committee.
Oxfam has railed against the wealthy. Certainly there is corruption and there are modern robber barrons. However, Oxfam has been far less effective than Bill Gates at raising people out of poverty. Oxfam is also less effective than Deng Xiaoping who was the Chinese leader who set China onto a path of rapid economic growth which has raised 1 billion people out of poverty.