How stop 999 millionaire from buying government and changing tax law?

We used t have “progressive” income taxes where higher income paid more, but tax breaks have largely gone to the wealthy over the last half century. While we still have tax brackets, they top off much lower than they used to. More importantly we have a really complex tax code, where some people are able to use loopholes and exceptions, such that many wealthy people pay at a lower rate. Were effectively a “regressive” tax code now

Over one billion? Way too fucking high.