Conqueror's Haki (or Haoshoku) is a scrapped ability that grants the player the skill to overpower the will of others, particularly weak-willed foes, knocking them on the ground.
It is a rare form of Haki, being not obtainable through training and only one in several million are born with it (One Piece concept).
The ability has about 3 seconds of startup, and lasts for about 12 seconds. After the startup, the player is capable of using any move on the stunned players. Its range seems fairly big, but it is currently unknown.
The few pieces of official footage appear to be very polished.
It's most likely going to be an Admin Spec.
There is a very strong backlash from the community towards this ability, as it deals an inevitable stun, being extremely overpowered in PvP. The way of acquiring it is also heavily overlooked.