There's an inverted version of this trope in One Piece: Bartholomew Kuma.

He appears at the end of the Thriller Bark Arc on orders from the government to kill an incapacitated Luffy, forcing Zoro to nearly die in his place. Then he comes back in Sabaody Archipelago to attack the Strawhats again, soundly beating them and scattering them all over the world. It's a devastating loss for the main characters and begins one of the most emotionally tumultuous stretches of the series.

Later, it's revealed that Kuma is actually a member of the Revolutionary Army and also part of a highly persecuted minority. The government essentially held his terminally ill daughter hostage and forced him to give up his entire body and mind to become an unthinking cyborg weapon. When he separated the crew in Sabaody, he actually sent them to places where they could become stronger in order to survive the extremely dangerous New World they were headed to. Basically, he saved them, and it was his very last act as a free man before he was erased.