Bad Ending: Natasha pushes Bruce into a pit (a pit within a floating city), thus taking away his choice to do something he openly fears. Bruce has no agency, Natasha is painted as a hypocrite, since you’d think she would know what it’s like to have her agency taken away and being forced to do things she’s not proud of
Good Ending: Natasha gives up on trying to convince Bruce to Hulk out, grabbing his gun and walking out (so then we get that badass walk that the trailers PROMISED US). bruce waits a beat, decides ON HIS OWN what he should do. then as natasha reaches the exit, she hears stomping behind her. a parallel to the first avengers movie with her face off with the hulk, except this time, she turns and he's standing behind her, grinning, ready to go to battle with her. then she's all "let's go, big guy." and she rides on his back to where the battle is happening