Genuinely one of the most boring movies I've ever seen.
As a fan of both suspense and storytelling, I understand that a tone needs to be set to enhance the climax of the story, but there is no discernible climax imo. I kept expecting something of significance to happen, and it didn't. Even his monologue in the first few minutes was bearable. However, the film just doesn't pick up any traction.
Characters are introduced and then never play another role in the story (not only the ones he kills). Between the ludicrous amount of product placement throughout the film and the the protagonist constantly telling himself "anticipate, don't improvise" while never really anticipating much, The Killer loses its ability to build any sort of positive or negative relationship with Fassbender's character.
Unless you are able to enjoy a character purely because he is able to kill people (which I generally don't find an issue), you will not enjoy this film.
The only redeeming qualities are that Fassbender is a great actor and the fight scene was good, otherwise I'd have rated this as a 1-star.