This film proved to be remarkably dull and poorly executed. There's a complete lack of character development, the camera work is unnecessarily shaky, and there are extended sequences showing absolutely nothing. It’s never clarified who the central figure actually is. The young people who enlist him for fighting are portrayed negatively in a very unsophisticated manner. The storyline isn't really centered on the fights themselves—there are only a few scenes that are poorly handled—but instead focuses on a homeless man, his surroundings, and what seem to be imagined scenarios, utilizing an imaginary companion to… converse, I suppose. I’d even suggest the plot is essentially missing altogether. Ultimately, the director employs a predictable twist ending and loud music in an attempt to create an emotional impact. The film currently holds a rating of 7.9 on another website, and there are no reviews here yet; I'd like to award it half a star to correct this, but "Cardboard Boxer" is simply awful. I’m disappointed that my review hasn’t been helpful to many people. Reflecting on it four years later, I still believe it accurately describes the movie. I am transferring my reviews from another platform which has deteriorated into something of low quality. TMDB seems great and I'm excited to participate here.

Source on TMDB