In my understanding, from reading the book, Rethinking Narcissism, the opposite end of the spectrum is what the author calls echoists. People who have such a lack of sense of self that they constantly shift themselves to be who they believe others want them to be.

Echoists really struggle with setting healthy boundaries, tend to be rescuers or fixers on the drama triangle and over give to the point of self-sacrifice and martyrdom.

Many highly sensitive and empathic people fall into this category, especially if they had a narcissistic parent, until they learn that valuing and focusing on their own needs does not make them selfish, but instead healthy.