Kamui is the most overpowered ability, granting intangibility and teleportation to its user.

Source: https://gamerant.com/naruto-who-had-the-strongest-mangekyo-sharingan-ability/

While it does not offer him the same elemental intangibility that Logias are famous for -- and actually makes him much more susceptible to damage than he would be without it -- Blackbeard clearly stated that its other abilities more than make up for it.

Source: https://www.cbr.com/one-piece-blackbeard-multiple-devil-fruits-theories/