Haō-shoku no Haki
Haoshoku Haki (覇王色の覇気 Haō-shoku no Haki) is one of the three types of Haki, as well as the rarest on all three.
Haoshoku Haki is a rare form of Haki that cannot be attained through training and only one in a million people carry it.
This type of Haki grants the user the ability to dominate the wills of others, as well taming monsters. The most common usage in the series so far is knocking those with weak wills unconscious. Whilst inexperienced users are restricted to merely overpowering the will of one individual or blindly knocking out weak-willed people around them, those with more expertise can pick out weak-willed individuals in a large group and knock them out without affecting those around them. However, those with stronger wills can resist or even ignore the effects of Haoshoku Haki. According to Rayleigh, while this type of Haki cannot be attained through training, it can be improved through training, as it grows as the user's spirit grows. The ability to knock someone out depends on the difference in strength between the person using Haki and the person or persons the user is trying to knock out. The greater the power gap, the easier it is to knock the victim out. It seems that upon recovery, victims of Haoshoku Haki experience the sensation of chills running through their body. However, it presumably wears off after a short period.