I think the death penalty should really only be allowed for mass murder / enslavement.
However, I doubt any billionaires are innocent of enslaving people, even if it’s “I paid them ($0.07 / day, which is slave wages)!” So, fuck the ultra rich. They didn’t get there by hard work; they got there by exploiting people and the system. Finances are not unlimited, so funneling that much money to yourself means you are directly depriving whole communities of livelihood and, almost always, actual life.