Occasionally, you get a hero with such personal magnetism that he is capable of persuading others, usually the Badass Bystander, to join him in his quest. Of course, the new companion has no qualms about killing for, or even dying for, the hero, despite having known him only briefly and facing many people who want him dead.
This is a staple of fiction that may well be Older Than They Think. Many epics and legends chronicle the process by which a hero gathers a band of motley friends and allies of dubious background but doubtless courage and nobility. Even if the hero has no special quality compared to his subordinates, this is often his implied "power", Heart.
There's a few variants of this:
Beat them up. Sparing someone's life after kicking their ass has a 50/50 chance of making them rethink their ways or at least earning their respect and maybe they'll eventually become a lifelong friend and ally.
Conversely, beat up their enemy along with them. Fire-Forged Friends are always ready to come along.
Give a kid a candy bar. Because hey, proving you're kind to cute orphans is the best way to get their Caretaker to dump them to come with you!
Save their life. Simple: save someone's life, or buy their freedom, and they'll be your slave forever!
Tell them your quest. Who knows? Maybe they too are out to put a stop to Doctor Demonica? A particularly idealistic or persuasive hero can pull this off with gusto on even the most jaded.
Often at the center of a Character-Magnetic Team. Contrast with The Dulcinea Effect, which usually involves the hero falling victim to a similar phenomenon at the hands of a member of the opposite sex, and Hitchhiker Heroes. A female Magnetic Hero who leads male characters with The Dulcinea Effect may be a Jeanne d'Archétype. On a larger scale, the usual subject of A Protagonist Shall Lead Them.
The resultant group generally turns out to be a Ragtag Bunch of Misfits. On a large enough scale, the hero will have created their own variation of The Cavalry or Big Damn Heroes. If it actually sticks around for a while, you may get True Companions or a Badass Crew.
Contrast Socially Awkward Hero and Hero with Bad Publicity.
Has nothing to do with a hero with Magnetism Manipulation, unless there's a Magnetic Hero with Magnetism Manipulation.