Bill Gates improved the lives of countless people around the world. He could as easily made the lives of countless worse if he wanted to or as an unintended consequence of his projects.
As an unintended consequence, sure, but that's more true of scientific/technological progress specifically than what Bill Gates did, which was closer to business and tech popularization. If a scientist invents a super-virus that kills everyone, then yes, obviously, they've made the world worse, but that's not really tied to money.
As for "as easily" making countless lives worse in other ways - I kind of disagree there. He made countless lives better because people voluntarily bought his products. He didn't coerce people, they chose to do it. There's no analagously easy way to spend money to ruin people's lives, and especially not if you consider the kind of scrutiny and backlash he'd receive.
My friends who work in public health research despise the foundation because they are absolute gatekeepers on what can and cannot be funded. If you are trying to do research that is not part of the foundations priorities, good luck, they say.
The Foundation is essentially only accountable to themselves and can have global impacts on health research distribution. A recent example is that their whims affected the speed and distribution of COVID vaccines.
https://www.politico.com/news/2022/09/14/global-covid-pandem...