Superman knocks out Giganta and she falls to the ground, but in all subsequent shots, including the pan-out overhead shot immediately following her fall, she is nowhere to be seen.
When Superman meets with Lex Luthor, Luthor extends his left hand to Superman when offering him to work for him, and Superman slams the car onto Metallo with the front of the car in the ground. When Luthor shows the footage to the public, Luthors right hand is extended, and the car is on its wheels.
During Lex Luthor's speech as president, according to flag etiquette, the American flags hanging vertically are draped incorrectly. The field of stars should be on the left hand side of the viewer.
When Power Girl attacks Major Force, in one shot from behind it can just be seen under her cape that her right leg is white all the way to the knee.
When Billy Batson says the word "Shazam" while fighting Batman, the subtitles misspell it as "Shizam."
Superman flies up into space to rescue Batman, who is in the wrecked rocket. However, this would be suicide for Superman because the Kryptonite dust cloud and the trillions of shards of the meteor would still be floating around out there.