This is actually a perfectly viable power set, now that I think about it. A Mary Sue is perfect, right? Since the world works on narrative tropes, the Aspect of Mary Sue would turn a character into a perpetually-escalating engine of success or failure. To be in tune with the Aspect, the character would have to actually BE competent, friendly, liked and knowledgeable. Every time they casually succeeded, they became more of a Mary Sue, and thus more in tune with the Aspect, increasing their power and allowing them to keep escalating their perfection. Yet, the moment they failed, they would cease to be perfect, and thus fail at being a Mary Sue. As a result, they would stop being in tune with the Aspect of Mary Sue and would start losing power, increasing their chances of further failure and the consequent loss of power, so on and so forth.
Basically, it'd be the ultimate Charisma build. If you convince everyone around you that you are perfect, you would receive the power to become perfect, but the moment you botch a Charm check, you start to lose power. So, you'd need to start doing rolls for Charm to arrest your own fall.