Well, it really depends on how you describe ruthlessness. In my eyes, most of them were pretty ruthless, even Ford. After his introduction of the assembly line, he was hiring and firing people at an astonishing rate. I can't remember the exact numbers, but I could look them up for you. Other's used tactics that were considered ruthless as well, such as trusts and other things. If I were going to use that thesis, I would just try to prove it.