Transmigrator And Regressor

It's a story about a main character that reincarnated to a novel world. At first he was seeking for a nice happy life but unfortunately the fate said otherwise. In the end he awakened a cheat like power that changed everything. No matter how many times he tried, there's always one more person to be saved until the only person he can't saved was himself. But that's not only it, when there is transmigator, there exist a regressor.