The depression in freezing points are in the order :
Acetic acid < trichloroacetic acid < trifluoroacetic acid
Fluorine,being most electronegative,has the highest electron with drawing tendency.
Consequently trifluroacetic acid is the strongest while acetic acid is the weaker acid.Hence trifluoroacetic acid ionizes to largest extent.
Thus depression in freezing point is maximum for the fluroacetic acid.