Like to share my take on the much ridiculed "Martha" scene in BvS. Spoiler: End of film many think the reason Batman spares Superman is due to finding out their mothers share the same name. I think it is more than that and I believe there was two thoughts going through the Dark Knight's mind: 1. Bruce's Martha may be dead but Clark's can still be saved. But that is the minor motivation. I think the main thought in his mind is 2. The moment Lois reveals Lex put Superman up to the fight by kidnapping Martha is when the World's Greatest Detective realized he had been a pawn of Lex's all along. Batman is furious at himself when he screams and throws the Kryptonite spear. He should have seen the signs. He should not have let himself be so easily manipulated. This I think is his main motivation through the rest of the film (& through SS & JL as well) is redemption.