A major weakness of Victor in Frankenstein is that like many tragic heroes, he has the flaw of hubris. Hubris is a term coined from Greek dramas that basically means extreme arrogance or pride. In Victor's case, his extreme arrogance or pride developed through his passion for science and his plan to take on the role of Creator.
In discovering the means to reanimate dead flesh and make the Creature, Victor challenged the natural order. He believed that he was worthy to "play God," and ultimately the result of Victor's foolish arrogance, the Creature, has a hand in Victor's tragic undoing.