I watched an episode of Metastasis with English subtitles on Netflix back-to-back with the corresponding Breaking Bad episode (S2E02 - "Grilled") and noted some of the differences that highlight the reduced quality of the adaptation. Here are a few:
This is the one with the cold-open showing a really weird flash-forward scene with Jessie's car bouncing in the desert and then the episode explains how the heck we got there. Part of what makes it weird is hearing that loud car bounce with it's hydraulics before we see what is making that obnoxious sound. Seeing it only raises more questions, like "why was the car abandoned like that?!". Metastasis immediately cheapens this by changing it to a car with the windshield wipers on. Big whoop. I could barely even hear them in the scene leading up to the reveal.
Tuco looks like a stereotypical middle-age mariachi band / migrant worker Mexican with a degree of male pattern baldness, day-worker clothes, and one of those upside-down U shaped mustaches that goes all the way down. His gangstah grille is laughably out of place on this guy! His crazy outbursts are like a normal excited person instead of a screaming maniac. When he shoots the cow they don't even show a cow. He just fires out the window and turns around to talk about the "cow" he just shot.
Tuco's uncle, Hector "Tio" Salamanca, looks way too young and not even remotely feeble. They made his fingernails look nasty to compensate but his "most interesting man in the world" beard still kills it. I don't know how they expect this guy to pull off the scene where he intentionally soils himself and the floor in the DEA office (next episode). He was so feeble in the original that it made no sense that Tuco expected him to feed himself, so I guess that is kinda fixed. There are scenes with Tio and Tuco's face right next to each other and Tio barely looks older at all. When Tuco rants about "old people" after misunderstanding Tio at dinner, it's hard not to laugh since Tio doesn't even look old enough to be Tuco's father.
Going back to the opening scene after the title cards, Hank just sticks Tuco's mugshot on a white board. In the original he lined the shot up with the head and shoulder outline of a paper target, symbolically making him the target. That was kinda important. The actor playing the Gomez role looks a lot like the original actor. It isn't set in the USA so Hank doesn't work for the DEA (of course) but it doesn't seem like some equivalent law enforcement office either. There is a conversation where Jessie's mom discovers Hank's DEA connection during his search for Walt and clams up momentarily as she questions Hank's motives. The conversation simply never goes there in the remake making it almost pointless. She had no idea he was law enforcement so it doesn't set any precedent for his future encounters with Jessie.
Hunting down Jessie's car with LoJack, was already far-fetched, but the adaptation has to rely on satellite anti-theft, which is something that you might find in a car that costs a couple hundred thou' (not Jessie's pampered classic car). During the final face-off Tuco was clearly out of ammo when the popped up and got shot by Hank, which makes no sense (why pop up and point an empty gun?). He had just reloaded in the original version.
The actor playing Walt Junior clearly isn't actually suffering from cerebral palsy, unlike RJ Mitte. I think they added a scene too because I don't recall seeing him feel under the sink and almost find a gun Walt his there. There's a missing scene too where Hank searches Walt's car for clues. Instead, he just walks in and states that he just finished doing that.
If it's not already clear, I'm using the original character names even though some changed (Hank became Henry, for example).