The Cluster B personalities

These personalities are defined by Wikipedia as:

[C]haracterized by dramatic, overly emotional, or unpredictable thinking or behavior or interaction with others. They include antisocial personality disorder, borderline personality disorder, histrionic personalty disorder and antisocial personality disorder. 

"Antisocial personality disorder" is another way of referring to sociopathy.

These disorders are grouped together for good reason, as they are indicative of character flaws, as opposed to either neuroses or psychoses.

If you're trying to figure out who's who in your personal life, it's helpful to think of narcissistic personalities as walking, talking egos (Donald Trump is the most prominent current example).

Think of histrionic personalities as walking, talking needs for attention (think Jim Carrey or Miley Cyrus or any number of Instagram personalities).

And think of borderline personalities as seething, volcanic bundles of rage (think Rosie O'Donnell or Rose McGowan).

A sociopath is in fact all these things; he is simply better at hiding them. He is as egotistical as any narcissist, though he likely affects a veneer of modesty.

He hates not being the center of attention in any group. If someone else is, he'll usually find a way to undermine him. But, he can bide his time about working his way back into the limelight.

And he may not appear to be a bundle of rage, but there is no one more full of schadenfreude. He is in fact constantly overflowing with animosity and a desire to see you fail -- even as he pretends to be your friend.

I've known narcissistic personalities who weren't full of rage (unless someone insulted them).

I've known histrionic personalities who didn't consistently overrate themselves.

Neither of the borderline personalities I've known personally (or have been aware of, at least) floated around on a cloud of egotism, or even needed to be the center of attention.

But I've never known a sociopath who didn't manage to incorporate all of these traits.