The gemara in Taanis 25B explains:
During a draught, Rabbi Eliezer davened 24 brochos from the amud and no rain fell.
Rabbi Akiva just said, “Our father, our king: we have no king except for you. For your sake, have mercy on us,” and rain fell.
People were saying negative things about Rabbi Eliezer.
A voice came out of heaven and said, “It’s not because Rabbi Akiva is greater than Rabbi Eliezer; it’s because Rabbi Akiva is maavir al midosav while Rabbi Eliezer is not.”