From many seemingly empty lines in the story of One Piece one is a clue to understanding a truth.
The phrase of Dracule Mihawk “One by one, he turns the people around him into his allies. More than anyone else sailing the seas… That man possesses the most terrifying power” that describes Luffy who not only had a small army following him but other people joining to help him during the Paramount War.
What is this “Power”? I would say it’s Haki, Luffy’s own will(power). To be specific his Conqueror’s Will.
As Rayleigh explained on Rusukaina you can’t train your Conqueror’s Will like other types of Haki, you can only learn to control it.
- You have to improve your character to strengthened it. So someone’s charisma and personality determine the strength of his Conqueror’s Will. By being mentally stronger man you will be a stronger “manipulator”.
- Conqueror’s Will overpower the will of you’re opponent. This could be seen as knocking them out as is always is, but what about the subconscious? I think that a strong user of Conquer’s Will is able to change the way people feel and think about something, influence there decisions.