When Marissa kills Hanna's grandmother, we see her from the front rolling her eyes and slumping to the ground. Also, she is standing in front of her daughter's (Hanna's mother's) photo. There is no exit wound or blood splatter shown. But later, when Erik and Hanna meet up in her grandmother's apartment, we see that Hanna's mother's photo has a bullet hole in it and blood splatter around it indicating that the bullet had exited from the front, which is inconsistent with what we were shown before.
In the extended conversation in bed between Hanna and her new friend, they are supposedly talking face-to-face because we see the back side of the other's head, however as the camera switches between them they are both shown lying on their left side making talking face-to-face impossible.
When Hanna first escapes the CIA base in Morocco, she is amazed at an electric light and overwhelmed by the boiling of an electric kettle. Yet a couple of days later, unaided, she can Google "DNA" and find out all about genetic engineering. Seems unlikely.
This is addressed in one of the deleted scenes which can be viewed on the DVD. When she walks into the internet café, she actually does receive assistance from an employee in how to use the computer.
During the final scene in the amusement park, Marissa is wearing shoes, but at one point she is seen wearing calf-high boots.
Hanna and Sophie lie on their sides in the tent, talking face to face. But in their respective close ups, both girls are lying with the left hand sides of their faces on the floor of the tent, and their right ears in the air, which means they can't be face to face. Sophie's close ups appear to have been flipped in editing for some reason.
The aircraft that Hanna sees flying over the cabin was a Lockheed C-130 Hercules. These aircraft have turboprop engines which use the exhaust of gas turbines to turn the propellers and that sound almost like a normal jet engines with a bit of a buzz from the propellers. The scene in question, however, clearly features the sound of piston engines.
In the freight yard scene, when Hanna kills one of the men after her, she slashes him several times across the chest, and then body slams him up against the wall. When she pulls away and runs off, there is no blood on her shirt or face.
During the final confrontation between Hanna and Marissa, Marissa is lying on her back with her feet closest to Hanna. Yet the shot from Hanna's viewpoint has Marissa's head closest to Hanna, with her feet pointing away, which should make Hanna look upside down from Marissa's viewpoint, but she's right side up on the screen as we see her.
Hanna was raised by her father, in isolation, near the Arctic Circle, intensely trained to be an assassin. In a close-up of Hanna she has pierced ears, it is unlikely from her upbringing that she would have this.
When Hanna is escaping from the underground base she fires a gun and the slide locks open indicating that it is empty, but she is seen and heard to keep firing.
When Rachel is driving and talking to Hanna, the sun is outside Rachel's window but in the reverse shots the sun is outside Hanna's window as well.
In the first shot at the CIA, there are two sets of flags, one U.S. and one other flag in each set. In one of the sets the U.S. flag is properly on its own right. In the other, the U.S. flag is on its own left - a serious breach of flag etiquette that the CIA would have been highly unlikely to have committed.
The bridge in the background where Eric leaves the water, is the Femer bridge in Germany. When he comes up he kills two Danish police officers and later is seen lying on a bed reading a postcard, where the address says Aalsgaarde, which is a city in the northern part of Zealand, Denmark.
Hanna's cover story is that she lives in Germany, however she mispronounces the type of school she attends. In the German language, "Gymnasium" is said with a hard g ("guh"), rather than a soft g ("juh") as in English.
When Hanna jumps in the river after the chase in the container yard, Isaacs is wearing his yellow jogging suit, without blood on it. When we next see him while Marissa is interrogating the family, he is flipping a section of steel pipe end over end in his hand, but his jogging suit is spattered with blood. All the family members are still alive, so where did the blood come from?
When been driven in the suv, you can see Hanna has 2 puncture holes in her ears where studs have been.
When Sebastian wets his hair it switches from forward to spiked.
Hanna has been carefully prepared to kill Marissa, but never shown a photograph to identify her.
At around one minute, there is a stag galloping on snow making a noise as if it is galloping on medium hard ground, not snow.
Hanna goes out on a date wearing a glittery silver masquerade half mask which later turns blue and then back to silver again.
When Sophie refer to the two Spanish boys she fancies, the next shot shows the boys at a Foosball table. The immediate shot (without going back to Hanna and Sophie) shows them on opposite sides of the table.
The postcard Erik is reading has multiple faults in the address. First, the word for boarding house is written in an incorrect German, "Gaest Haus". In Danish it would have read "Gæstehus". Second, the name of the boarding house, which translates into English "The Beautiful Mermaid", has the last part of "mermaid" written in German ("fraue" instead of the Danish "frue"). Finally the postcode (zip code) is wrong, stating 8129, whereas it should have been 3140.
Erik decides to swim from Sweden to Denmark across the strait between them (Øresund), presumable to avoid border checks. But not only are both Denmark and Sweden (as well as Finland) members of the EU and also part of the Schengen Area, he could have traveled uninterrupted by land or sea from Finland to Denmark due to the Nordic Passport Union, using public transport. His method of entering seems a bit odd, as he later in the film arrives in Berlin by bus.
When we see Hanna after she has been captured there are four shots showing her lying on the table. In the top two shots her right leg is on the bottom of the left leg but in the bottom two shots her right leg is on the top of her left leg.
When Marissa is returning fire through the door in the hotel room, the slide of her gun locks back, signifying an empty magazine. However, in subsequent shots, she continues to fire, even though she is never shown reloading her gun.
Hanna has been trained to sound like an official document, rather than a plausible narrative that a lone teenager might give.