The episode received mixed reviews from critics. The development of the characters, and performances, especially from
Greg Austin,
Katherine Kelly, and
Jordan Renzo were praised, but many reviewers felt that the episode was too fast-paced, and did not feel like a satisfying conclusion for the season's storylines.
Entertainment Weekly's Nivea Serreao and Kelly Connolly both gave a positive review, praising the episode's stakes, twists and characters, especially Tanya. However, Connolly stated that it was "so overloaded with death-or-death problems that little moments never have a chance to land."
Doctor Who TV called
Class "a finale that not only addresses the necessary narrative requirements, but does so in unexpected ways, shaded by the writer’s personal agenda, that inform
Class ultimate message." They praised the writing of the characters, and that "The complete destruction of the entire Shadow Kin populace is portrayed not as 'justifiable' but as necessary." However, they thought that the episode "leaves too many logistical questions unanswered, and several characters see little resolution to their character arc." They concluded by stating "Overall,
Class is a remarkably efficient, seldom-rushed, eight-episode series; however, in trying to generate compelling interest in a second series, Ness’ script for 'The Lost' feels irresolute. Such a dense narrative needed a proper epilogue, a ninth episode."
Flickering Myth called "The Lost" "a disappointing finale to
Class – one that, ultimately, is unable to deliver upon the promise of the series as a whole, and leaves the show’s future looking rather uncertain." They heavily criticized the fast pace of the episode, calling it "a real tonal mishmash that can only be described as a disaster". Regarding the ending, they stated that it "confirms the growing suspicion that the Governors were a far more interesting antagonistic force than the Shadowkin could ever have been – something we hadn’t seen before, something new, and by extension something exciting. And this is very much the wrong note to end the episode on – and indeed the wrong note to end the series on. In some ways it feels like a dismissal of what’s gone on before, an entirely unearned moment of saying "actually, all the good stuff will be next year". However, he praised the performance of Katherine Kelly, and the characters of Charlie and Matteusz.
Cult Box gave a very positive review, stating that
Class "has beaten its own path rather than relying on elements from the main show. However, with the creative vision that Patrick Ness has demonstrated throughout, we have faith that he will put a new spin on the killer statues and we look forward to seeing where he takes them and Coal Hill Academy in the future." In a moderately positive review,
Vodzilla called the episode "violent and emotionally wrenching" and praised the treatment of the characters of Charlie, Matteusz and Quill, but also called it "dramatically limp".
Mym Buzz gave a positive review, considering that "'The Lost' offered up an incident-packed, revelation-rammed, fast-paced, visually spectacular season finale – and there were lots of really fun moments, exquisite character exchanges and big dramatic gestures to savour". However, they also called it "a frustratingly vague viewing experience" that " didn’t feel like a climax so much as prologue. It’s great to leave the audience wanting more, but not only because it doesn’t feel like you’ve given them enough."
Den of Geek felt that the finale "didn’t let up in intensity", but suffered from "an excess of urgency and earnestness. When every note is emphasised and there’s no dynamic range, the result is… tonal blandness." He praised the show's tendency to kill off characters and not backing down, stating "You have to admire that kind of gutsiness. Tentative? This show doesn’t know the meaning of the word." ==References==