Which superhuman character (or species) has the most poetic weakness?S

Science fiction and fantasy are full of unstoppable badasses. But often, they'll have a weakness that is fairly poetic. Superman is vulnerable to the ruins of his own home planet. Sontarans can never turn their back on you. But which character or group has the most poetic weakness?

Please include a picture or clip of this nearly unstoppable creation. And mention the name, and where he/she/they come from. Thanks!

Image via Superman8193.