At Marineford, Luffy was separated from his crew, gave up the chance to see them, fought enemies way too powerful for him, poisoned,  had his life span reduced several times all to save his brother and managed to save him only to lose him minutes later in circumstances beyond of control, then was brutally injured, which led him to being the closes to death than he had ever been, only to be saved by Law

In Dressrosa, Law has been separated from his crew for a long time, willing threw way the security and power of being a warlord, had life threatening injuries and loses a arm as well as have his life span shortened all for the save of avenging and fulling Corazon’s wishes and stop Doflamingo, which would have been successful if Doflamingo by luck managed to stitch his organs together, only to be saved by Luffy.

Both Luffy and Law saved each other at their lowest point.