After Batman shoots Reverse Flash through the head, Flash rushes over to Batman and catches him before he falls over from his wounds. As Flash is lying him down slowly, there is no blood on Batman's face. It then cuts to a close up as Batman reaches up to pull off his mask and there is suddenly blood on his lips and chin.
After Aquaman finds Orm dead and sees the carnage of the battle, Wonder Woman comes up behind him and stabs his back with her sword. He falls to his knees and she walks around in front of him, and as she does you can see there is no blood on her sword. But then she holds the sword to his neck in a close up and suddenly the sword is covered in Aquaman's blood.
After dodging a low attack, Wonder Woman jumps into the air and slashes down at Aquaman with her sword. Aquaman raises his trident and blocks the attack, but is only holding the trident with one hand. It cuts to a close up and instantly Aquaman is two handing the trident.
Wonder Woman tries to stab Captain Thunder with her dagger and just breaks it on his chest. She then has to drop the broken blade to catch his fist as he tries to punch her. She then uses both her hands to use her Lasso of Truth to make him say Shazam and change his form. The lightning bolt hits her and she flies off him as he reverts back to 6 children. As she stands up, the broken dagger is suddenly in her hand again.
After fighting for a brief few seconds, Black Manta kills Deathstroke by burning a hole through his chest with his heat vision. Deathstroke falls right next to Lex Luthor as his chest sizzles and his swords fall around him to. A couple shots later as Black Manta is picking Lex up, Deathstroke's body and swords have vanished.
After Lex Luthor and Deathstroke step out onto the deck of Deathstroke's ship, Ravager and begin talking, Aquaman's sub surfaces and smacks into the Ravager and it shakes violently and lurches. Yet the crew, Lex, and Deathstroke stand perfectly still just moving their arms around a bit. An impact on a ship like that would send all people standing up falling everywhere with no balance.
Superman begins shooting his super intense heat vision at the soldiers attacking him and the other heroes. His vision cuts boats in half, and incinerates the soldiers into ash in an instant. The lasers from his eyes are super strength, with him not yet knowing how to hold any of it back or shut it off, and it is going through the soldiers and boats. Yet the vision leaves no damage at all to the ground the soldiers were standing on, nor does it create any steam when going across the water cutting boats in half.
Young Barry discovers the murder scene of his mother and stands in shock in the doorway. The light fades showing the transition from day to night and there are forensic scientists around the scene and cops analyzing it and asking people questions. Barry is still shown there at the door watching as his mother is put into a body bag. The police would not have kept him there to see that and would have taken him away to be questioned as soon as the place became a crime scene. Barry would most likely have been the one to call the police about the murder, meaning he would have had to return to that spot, so the police would have taken him away. And even if someone else called and Barry stayed in that exact same spot, trauma councilors would have been called to come and take him away for counseling. Either way, Barry would not have still been at the scene at this time.
When the rest of the Justice League arrive at the Flash Museum, Captain Atom vaporizes a section of the wall to allow him and some others to enter. The hole shows 3 layers to the wall, the inner wall, the outer wall, and a middle apparently metal center section. There are several circle like spots around the hole in the center part of the wall. They are all perfectly round, despite being in any given direction around the circumference of the opening. This is wrong. The circles would be caused by structural bars inserted in the layer, and they would all have been either vertical or horizontal, and thus the circles would not be circles all the way around, but changing to elongated and shorter depending on where they were on the opening. Yet all are perfectly round. This would mean that the all the bars were in all different directions and converging in the center of where Atom just happened to make the hole, which would never be the case.
Batman shoots Reverse Flash in the head, and the camera pans up to show the hole through his head with Batman on the other side. The hole's entrance and exit wounds are the same size. A bullet wound would never be like that. As the bullet passes through flesh, it pushes flesh before it, making the wound bigger and bigger the deeper it goes. The exit wound is always quite a bit bigger than the entrance. The exit wound does almost appear larger from this shot, but that is just the illusion of the wound coming towards the camera.
After the fight at the Flash museum, all the Rogues have bombs placed on their persons. Instead of leaving with the villains, the heroes could've simply had them take off their costumes and dispose of the explosives, as Wonder Woman eventually does with Captain Cold's belt. None of the bombs were embedded in flesh. Reverse Flash explicitly said taking off their belts would detonate the bombs.
When Flash, Batman, and Cyborg walk into the cell that is holding Superman, a shot of just Superman's legs show that they are down with his knees on the floor. It then cuts to an angle from the trio and suddenly his legs are bent up and his knees in the air. Given the size of the chamber, and the time it took them to walk across it, Superman would have had the time to roll over, to face the other direction.
How does the government know about Superman's weakness to the red sun??? It's assumed that they captured him when he was a baby, but how did they figure out before he was able to escape??? This is not explained and is just left unexplored in this film.
After regaining his powers, Barry assumes the reason he cannot run through time again is because the Speed Force is being shared with Thawne and limiting Barry's power. However, Barry was able to go back in time at the start of the film while Thawne was still alive and was consuming Speed Force in the original timeline.