Did I despise MS od the 90s and their business tactics? Sure. But wether he pays taxes on his philanthropic endeavors doesn't really matter, what matters is that they exist and do some good in the world -- and certainly, spending money on health care is good in my book. So what makes him a "dark character" in your eyes?
Instead of donating to existing public health (and education) organizations, OS programmer Gates created his own so that his personal biases wouldn't be challenged.
@BeatLeJuce You don't have to go very far online to find the answers to you question. James Corbett has amassed a formidable array of facts and history, for example.