That’s an interesting question, Yuriy, from a philosophical perspective. Researchers are investigating what they believe is a genetic component to the Dark Triad. Serial killers are generally believed to be either psychotic or among the Dark Triad spectrum. So I’m not sure an average person could ever meet the person they “could have” become and discover they could have been a serial killer. Those tendencies show up much earlier.
But for sure, we always have multiple paths we can take. If I were to meet the person I “could have” become, I think there are different people I could meet. Some that achieved far more, and also some that achieved far less.
For me, the quote is a good reminder to always strive to be all that I can be, and not to fritter away the days I have on this Earth.