We ask "what good can one person do"? We might also ask "what bad can one person do"? There are many one persons who changed things. Right?

Those who left a mark on the world. For better or worse? It's subjective. There is no unanimity among people bout what constitutes better and what constitutes worse. Whatever benefits some will harm others. Seldom do we find anything or anyone that benefits or harms EVERYONE. Can you think of any exceptions?