I’d argue that Herschel Walker was the worst. Although the others mentioned were bad, I think both parties knew what they were getting and giving up. I believe Mike Lynn didn’t understand what he would be giving up when he acquired Herschel. While giving up a boatload of valuable roster players, he lost both them and the draft picks he promised if those players weren’t on the Cowboys roster the next year. Jimmy Johnson cut or traded all of them and used those picks to build a dynasty. The Vikings slumped. Walker wasn’t a great fit in the Vikings offense. Mike Lynn became a laughingstock. It’s still the measuring stick for terrible trades.