There's also the offshore financial system, where entire islands are dedicated to helping billionaires avoid taxes. For example, the South Pacific Cook Islands literally specialize in helping wealthy people hide assets from creditors.
Of course, this was partially exposed in 2016's Panama Papers and this year's Pandora Papers.
And there are "evil" billionaires. The billionaires mentioned here are from the western world. In some countries (i.e. UAE) billionaires treat their workers like slaves. I admire Elon Musk very much for what he achieved, it's almost superhuman but contribute to society by paying taxes!