Plot hole: Where did Cross get the blood on his hands? The gloves were clean of blood after he looked at the teeth and removed the gloves, so where did it come from?
Continuity mistake: Near the end of the film, Violet infiltrates the complex and makes her way into a white room with tons of men in white suits. She starts fighting them and when a couple of guys come at her, she moves quickly and one guy stabs the other in the chest. When she goes to elbow one of the guys in the face, watch his helmet, it comes flying off, revealing his head and hair. When the camera quickly changes to another angle, his helmet is on perfectly straight. (01:17:45)
Revealing mistake: You can see the charges to break the glass armor at the chest of the first guard when Violet kicks down in the vault. (00:16:30)
Continuity mistake: When Violet holds her hand up to catch the sword, it's fine. But after she stabs the guard, both her hands are cut open in three directions. Also, she doesn't leave any blood on the sword itself.
Continuity mistake: After Violet's hologram says: ''You won't have him.'', Daxus tries to punch her, but he only strikes air and thus keeps moving, and nearly trips. He then gets back up, and in the next shot he gets up again. (01:06:50)
Continuity mistake: Violet smashes a few of the guards arm-mounted armor platings, but these shards disappear, and are never seen on the floor.
Revealing mistake: During the motorcycle chase, when Violet is on the building, the chopper gunner badly damages the exterior of the building, with brick and glass particles flying all over the place. But these particles disappear without a trace when they've moved a few feet away from the camera.
Continuity mistake: Violet deflects the incendiary gel with her sword, covering the tip of it with the gel. For the rest of the fight, the gel is gone, but when Daxus closes the blinds, it reappears, only now covering the entire sword. (01:23:35)
Continuity mistake: Daxus drops his gel gun, only to change it for a sword. But in the overhead shot of Violet and Daxus, the gel gun is nowhere to be seen. (01:23:50)
Continuity mistake: When Violet disassembles the AR-15, the buttstock is still in place. For the rest of the scene, the stock keeps reappearing and disappearing. (00:17:15)
Continuity mistake: When Violet jumps off of the building, she makes severe cracks in the concrete tiles. In the overhead shot with the dead guards, those cracks are gone. (00:20:25)
Audio problem: Daxus is about to cut open Six's head with the circular saw, and he stops when he hears the alarm. In the next shot, the saw isn't spinning anymore, but is still making a noise. (01:16:50)
Continuity mistake: In the chapel fight, during the first attack, she decapitates a few of Nerva's men, and in the shot of Violet's back, you can see those heads flying through the air. But in the shot from above, all the men still have their heads, and no heads can be seen lying in the middle of the circle.
Revealing mistake: During the fight with the men in white suits, all of these men use swords. Violet disarms a few of them, using then to cut or stab them with. But every time she slices, or better, tries to slice, you can see that the swords never actually cut, but are used as a sort of baseball bat. Also, they are sharp enough to cut someone, because Violet's hands are all cut open at the end of this fight scene. It simply means that these swords are blunt props, and that nobody did anything to make it appear that they are real.
Continuity mistake: When the guard with the customized AR-15 enters the room of the case, there are several guards directly behind him. However, Violet has plenty of time to disarm, kill him, and slowly turn around, upon which the guards reenter the room. It is not possible that they have been shot; the gun wasn't anywhere close to pointing at them.
Continuity mistake: When Violet tries to shoot the guards of the case, we get a close up of Violet pulling the trigger, only to strike an empty chamber. You can see the normal safety pin, and another flat circle. But when she disassembles that same gun moments later, the flat circle has turned into a knob.
Continuity mistake: In the scene where Violet and Six finally make it out of the building, they get into the black car with the door open. When Violet tells Daxis he's full of shit, she puts the car into drive to knock out the men behind her with the door closed. When she's done the door is again open.
Other mistake: Why are the guards carrying that useless glass armor? Glass is very heavy, so it is not comfortable; the armor isn't shock proof, because it breaks even if they just fall down; and it isn't bullet proof, because the guy with the AR-15 shoots right through it.
Chosen answer: Simple sex-appeal, no plot significance.