Arc Fatigue: For many people, the fact that Pérez-Reverte is so damn slow at releasing the next installments of the series (earlier ones used to be published within three years of difference, but five whole years passed between the sixth and the seventh, and the last to date was published in 2011) is a huge point of contempt.
Germans Love David Hasselhoff: Despite it was poorly received in Europe and America, the movie was absolutely loved in Asia, to the point that Chinese popularly call it "THE Spanish Film".
WTH, Casting Agency?: Often cited by critics. While some portrayals were considered okay or even good, most notably Quevedo (played by veteran actor Juan Echanove) and Alatriste himself (portrayed by Viggo Mortensen), the rest was rather weak. The most bizarre point was having Bocanegra played by a woman, nothing less.
Bile Fascination: In an almost unprecedented case in Spanish TV, viewers actually complained that Telecinco opted not to broadcast the last few episodes of Alatriste despite how furiously they dissed the series up to that point. Yep, it came a point in which people actually followed the series for how awful it was.
Squick: Angélica offering to pay Íñigo with sexual favors is admittedly an element from the books, but in this adaptation, her actress was 14 years old and his was prepubescent.
So Bad, It's Good: Even if the series was right there with the Eragon film when speaking about book adaptations, its general ridiculousness and shoddy making made it actually rather entertaining to see.
The main fan uproar came due to the series removing what they saw as the most important element in the books, the relationship between Alatriste and Íñigo. In the books, they are literally a case of Like a Son to Me, and the boy's loyalty to him is such that his only reason to be a soldier is to follow the captain to Flandes. In the series, however, Íñigo is completely indifferent to Alatriste and only sticks with him in order to become a soldier like his father, while Alatriste only sees him as a annoyance.
In the series, Angélica receives much more characterization than in any of the books, but only in exchange for turning her from a smart and sultry Fille Fatale to a parody of herself who never gets anything right and is tooled by everybody in the cast, even Íñigo himself.
The fact that the series contains so much humor despite the books being almost completely devoid of comedy was not better received, especially after checking that some legitimately badasses, like Quevedo or Sebastián Copons, were reduced to Bumbling Sidekick roles just to add Plucky Comic Relief.
The books emphasize the Combat Pragmatist philosophy of the characters, often showing Alatriste's derisive thoughts on show-off opponents and foes who do too much Weapon Twirling and Rule of Cool. In the series, he does exactly that, as the duels are often overtly spectacular or bizarrely choreographied (with instances like Quevedo chokeslamming a mook, Alatriste doing spinning back kicks and beating swordmen while barehanded, and characters doing the occasional Zorro sword trick).
WTH, Casting Agency?: The cast was panned by fans and creators alike, noting that it genuinely looked like the casting staff had chosen the worst actor imaginable for every role. Carmen Sánchez and Marcos Ruiz for Angélica and Íñigo were graphically described as looking like "kids chosen by nepotism for a school play", and Luis Callejo as Luis de Alquézar was considered by many as the equivalent of Count Dooku being played by Jack Black.