C-type asteroid
The largest unequivocally C-type asteroid is 10 Hygiea, although the SMASS classification places the largest asteroid, 1 Ceres, here as well, because that scheme lacks a G-type.
Potentially hazardous object
With a mean-diameter of approximately 7 kilometers, the Apollo asteroid is likely the largest known potentially hazardous object, despite its fainter absolute magnitude of 15.2, compared to other listed objects in the table below "(note: calculated mean-diameters in table are inferred from the objects brightness and its (assumed) albedo. They are only an approximation.)". The lowest numbered PHA is 1566 Icarus.