Another FBaWtFT project, I know. SPOILERS FOR FANTASTIC BEASTS AND WHERE TO FIND THEM BELOW!!! I I I V Here it is! The way I knew Dumbledore would k1ll Grindewald even before he does! (If he does: I haven't finished the movie yet) Grindy has the Elder wand (the most powerful wand - one of the Deathly Hallows), and I know from Harry Potter that you can only have the Elder wand if you disarm/kill the previous bearer. Now the way I know that Dumby kills Grindy is because during the time of the Harry Potter series, which is a few decades after this, Dumbledore's wand is the Elder Wand (until Voldemort takes it off Dumbledore's grave). Also, if Dumbledore simply disarmed Grindewald and got the Elder Wand, Grindy would have immediately killed him, hungry for his power back. So I expect that sometime in the movie, maybe later in this scene, they have a sappy final moment and then Dumbledore kills Grindewald.
Fantastic Beasts and Where to Find Them is by J.K. Rowling. SPOILERS BELOW!! I I V EDIT // I just finished the movie. Grindy doesn't die at he end, but Dumby sets out to kill him. I've researched and apparently Dumby kills Grindy in a final life-or-death battle. So I was right. Sort of. It happens after the timeline of FBaWtFT but it happens.