Powers & Abilities - Who used haki and who not?

We know prior to the timeskip we did not see hardening or CoA at all. CoO at least was hinted at (breath of all things, skypea, all the sensing/feeling

Do you have to be born with conquers haki, or can anyone learn it? - Quora

Powers & Abilities - The terrifying power of conqueror's Haki

Powers & Abilities - Is Luffy just using Basic Ryou + CoC? Is there a Level 3 Armament Haki/Internal Destruction CoA?

Limitations of Armament-Haki : r/OnePiece

One Piece: All Haki Types and Its Subforms (Explained)

Powers & Abilities - Who used haki and who not?

Every Straw Hat Pirate Who Uses Haki In One Piece (& How They Awakened It)

Can Luffy turn someone into rubber even if they have stronger Haki than them? - Quora

1039 Spoilers) You're Wrong About Haki - Understanding How Oda Writes Powers and Abilities : r/OnePiece

Powers & Abilities - A ton of people can do Haki blasts (not advanced penetrative Haki), Page 3