His ability to use Conqueror's Haki has been common knowledge since his time on Fish-Man Island, but following his battle with Kaido on Wano, his mastery over the technique has reached all-new heights.

Source: https://www.cbr.com/one-piece-conquerors-haki-users-ranked/

Kid was confirmed as a user of Conqueror's Haki by Kaido.

Source: https://gamerant.com/one-piece-all-conquerors-haki-users/

This makes it an incredibly dangerous subtype of Conqueror's Haki that can be a defining factor in combat.

Source: https://gamerant.com/one-piece-every-haki-sub-type-explained/