Collectively all large corps in America have too much power, so i’ll assume we mean “more power than the other corporations”
I’m that case I’ll believe that they’re “too powerful” when a tech company mismanages itself to bankruptcy and gets a bail out from tax payer funds. Or when other companies are forced by the government to use (and pay more for) software and tech from a specific company or group of companies (maybe software from “defense” contractors counts?).
Until then i’ll continue to believe that banks, coal, and oil companies have too much power.