Character mistake: In her first walk through the city with Dr. Ido, after feeding the dog her sandwich, Alita takes a flyer and reads it. Between the lines that read "Wanted" and "Murder" there is a line in Spanish that says "Querido para el asesinato." It should say "Querido por el asesinato".
Continuity mistake: During the game, Alita disposes of the black cyborg guy with the yellow paint, the same one she met at Kansas. She rips his arm off and uses it to spike the head of the colossal dude with the morning star-like weapon. You could see as the arm was being ripped, that debris and a big metallic piece of scrap were left behind. However, when the 2 next opponents are skating towards Alita making her take off fast, there is no such trace of debris beside the whole body of the guy. (01:33:00)
Continuity mistake: Alita and Hugo are talking; he just told her clumsily that she's heavy, and asks to see her hand. You can see walk past Alita a group of punks, but the same punks are also checking out of the stalls behind Hugo, with their colored purple and green mohawks visible in the background. (00:11:55)
Plot hole: Grewishka sneak-attacks Alita using his weapon from outside the window. How in the world was the hulking behemoth just standing outside the window without Alita noticing? He surely couldn't have tiptoed into that spot after she arrived, he makes a ruckus for every step he takes. (01:47:10)
Factual error: Grewishka consistently survives falling several stories down. He is twice the size of a normal human. Assuming that he maintains the same density (weight to volume ratio), the fall must still be 8 times (2×2×2 times) harder. A scientific breakthrough that reduces density is perhaps not far-fetched in a work of sci-fi. But here, Grewishka's demonstration of brute force suggests that he actually has higher density, not lower.
Factual error: Hugo detonates an incendiary device on Zapan's torso. Zapan's cloak catches fire, which he discards. The fire should burn (or at least blacken) his organic face and mohawk, but none of these happens. Zapan emerges completely unscathed. Most of his body is metallic - an excellent heat conductor. Zapan's organic parts should suffer serious damage. (01:27:25)
Continuity mistake: Hugo is running away from Zapan; after the sequence of Alita's busted pipe we see him jump over a parapet onto a street underneath, rolling just past an incoming utility vehicle. In the overhead shot he lands right in front of a group of people including a rather conspicuous man with a pink shirt, but in the following shot almost everyone in the street is gone. (01:34:40)
Continuity mistake: During the sequence when Alita manages to get her revenge on Tanji, look when she is coming out of the curve with enough speed to be able to tackle him. In between shots the crowd behind the ramp has completely changed, with some bearded guy and a dude with a panama appearing out of nowhere, to mention just the most obvious. (00:19:40)
Continuity mistake: Ido and his ex-wife are walking on a relatively narrow bridge with stalls on one side. When she says "clearly" to him admitting he did not destroy the body, a man with a backpack literally disappears between shots as he was walking past a woman in a white and blue shirt. (00:16:00)
Continuity mistake: In the first part of the walk through the streets of Iron City, many times the various passersby disappear and appear between shots - just look at the first cut, and how a punk dude is suddenly in front of Alita while they fail to pass by the bicycle lady that was going towards them. (00:09:15)
Continuity mistake: Alita and Dr. Ido talk in front of the sign of his clinic, and he gives her a name; during the back and forth of their dialogue, the passersby do not transfer between any shot and their reverse angle: they simply disappear (unlike for instance what happens behind the nurse with a purple shirted guy who shows up coherently turning a corner). (00:08:50)
Continuity mistake: During the battle with Grewishka in the alley, the brute punches a hole in the asphalt and one into the tiles and concrete wall. However, after Alita axe kicks him from above and slides behind him to grab Ido's weapon, there are good views of the alley and no trace of the damage is present.
Continuity mistake: As Alita has disposed of quite a few Hunters, the female called Screwhead and some black dude next to her with a yellow arm are shown in a closeup standing from their seats and prepare to intervene. But if you look back just a few seconds before at the beginning of the fight, Yellow Arm Dude was one of the first Alisha kicked to the curb, and Screwhead was standing already, blade in hand. (01:01:35)
Revealing mistake: After breaking Zapan's nose, Alita jumps on the table of two guys and trash talks them into a fight; before they attack, the two bottles of beer on the table are different, one being the generic red and white Cerveza, the other with a peach colored label. When she kicks the CGI bottles, those are two identical Cerveza ones. (01:01:15)
Continuity mistake: When Grewishka smashes through the floor of Kansas (the bar, that is) you can spot at the right side a couple of tables very close to the crater. When Alita follows him a moment later, the light table frame is even closer despite the hole being stable and nobody moving. (01:05:25)