Many have promised that when they die the money should be used for charity. Warren Buffet started this trend.
The bad part here is they can waste all the money however they want and nothing can stop them. Example, they buy cars just to blow them up, not one but 1000. They can afford it. Good for the environment? No, but fun for them as they might have found a new sport.
I don't mind billionaires existing, but I absolutely mind them getting special treatment and getting away with crimes.
edit: if you're mad about this comment, I have to think you're just jealous of the rich assholes. If billionaires paid their fair share of taxes and were prosecuted for crimes, the world would be objectively a better place. Instead, I guess for some that's not enough, it's a fully socialist world or NOTHING.