Ousting the founder-founder from the company and leaving it to non-founders, that's the worst decision any investor, co-founder, board member can make for a company. Good luck.
GM with Sloan would be a big one I think.
Many companies are at the end of their life cycle where the best thing they could do is manage the business well and return capital to shareholders.
Often founders act like it's their baby and don't want to let it die instead of fulfilling their fiduciary duties. You don't see many articles about how GE can't make anything new since Thomas Edison left.