Hypertrophy

Hypertrophy is a Quirk possessed by All For One, who stole it from an unknown person.

Description
Although never properly described, the Quirk seemingly allows All For One to enlarge his arm. Hypertrophy is described on Wikipedia as "the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number."