the virtues that I once possessed
The Creature acknowledges his fall from an original state of grace:
"virtues" seems to be deliberately Miltonic diction, invoking Satan
and Adam (and Eve). The Biblical context aside, this claim to a
prelapsarian perfection is intended to remind Victor of his own high
ambition (see 1.3.6) and to affirm how
well, on an internal if not external plane, it was realized.