The hatred between Trafalgar Law and Doflamingo dated back many years.
A man named Corazon had saved Law, only to pay for it with his life. To the still-young Law, it was no different from having the pillar of his life torn apart alive by Doflamingo. What was more, that man had been Doflamingo's own younger brother. Doflamingo had even killed his brother to vent his anger. If Corazon had not protected Law with his life back then, Law likely would not have escaped disaster either.
Over all these years, for the little boy Law had been, nothing had been more painful or cruel than losing Corazon, his spiritual pillar. Amid the ice and snow, that lonely, helpless little boy had wept himself hoarse, carrying despair toward life and the agony of losing a loved one. Beneath so many crushing blows, Law had endured, survived until today, and buried such deep hatred within himself.
Hikaru had no doubt that the desire for revenge was the belief that had kept Law alive all this time.
So after hearing that he had defeated Vergo, Law surely wanted to pull him into this and deal with Doflamingo together. After all, Hikaru's strength was plain to see. He had easily defeated Law and Vergo, so Law firmly believed he had the power to defeat Doflamingo.
Was that why Law had decided to join his ranks?
Hikaru quickly considered the various possible decisions Law had made in that instant. Revenge was undoubtedly Law's highest priority right now, but how sincere was his submission to Hikaru?
A faint smile rose on Hikaru's lips. People who valued their bonds were often hard to win over, but once they trusted someone, they would even be willing to lay down their lives for him.
Uchiha Hikaru decided not to