En Tayutai

En Tayutai also known as Smoke-Eater, was a former Pro Hero and the sixth user of the One For All Quirk. En is a reserved but friendly individual. He is well-aware of the limitations of his Quirk, guiding Izuku on how to best use it in conjunction with his other Quirks. Given that he resisted having One For All stolen by All For One, En presumably has extremely strong willpower.