My understanding is that the Bill & Melinda Gates Foundation only works on projects that are very transparent in their costs and minimise the risk of corruption siphoning away the money. No system is perfect but when I worked in international aid they were always the stick other orgs measured themselves against.

I think the general opinion of Bill Gates would be very different if he'd used his billions to hire mercenaries and overthrow governments, even un-elected ones. (Then again, Ross Perot did something close to this to rescue a few staff in Tehran and was hailed a hero).