I keep going back to one quote that probably isn't considered his most iconic, but it sticks with me. It's from his childhood, after Cora-san sacrifices himself. Law tells Doflamingo, 'I won't forget this day.' It's not flowery or grand. It's a raw, child's vow made from pure grief and rage, and it becomes the entire engine of his character for the next decade.
That quiet, simmering promise is what makes his later defiance so much heavier. When he finally stands before Doflamingo on the bridge in Dressrosa and says he's there to end the 'Age of Doflamingo,' that's the payoff. The inspiring part is the sheer endurance of his purpose, the way a single, traumatic moment crystallized into a will strong enough to take down a king. It’s grim inspiration, but it’s real—it shows how a person can be forged by their lowest point and choose to direct that pain outward, not just inward.
His line about the 'Will of D.' being the 'Natural Enemy of God' is cool and all, but for me, the real weight is in that simpler, earlier vow.