A couple of "radical" suggestions:

i) create a foundation to deal with a specific major issue facing society and start working to address it yourself or hire someone to be the primary day-to-day manager;

ii)  with legal advice, donate it to government with the explicit requirement that it has to be used to either:  i) pay down existing debt;  or ii) contribute to building critical infrastructure.

 Take inspiration from people like Andrew Carnegie (among other things, he funded libraries in English-speaking countries in order to support learning and education) who gave away over US$75BN of his wealth (in today's US dollars) WHILE HE WAS ALIVE and then another US$30BN after he died.  Don't just sit on huge piles of cash you don't need waiting for it to be taxed, or worse yet, for society to break down -- which it will do if things continue they way they are going.   Even the largest global philanthropists today (think Gates, Branson, Buffett etc)  pale in comparison with Carnegie.