WARNING: Spoilers for Army of the Dead.
Does Dieter die in Army of the Dead? Portrayed by German actor Matthias Schweighöfer, the character saves the life of his comrade Vanderohe (Omari Hardwick), but then appears to be the latest victim of the Zombie King, Zeus (Richard Cetrone). Since Dieter's death isn't shown on screen in Army of the Dead, there's evidence to support the theory that he's still alive.
Dieter is one of the most entertaining characters in Army of the Dead. As a safe cracker, he values silence while doing his work, especially when trying to unlock the "Götterdämmerung" vault at The Olympus in Las Vegas. Dieter repeatedly screams with a high-pitched voice in Army of the Dead; however, a climactic act of bravery shows his true nature. In the film's final act, he locks Vanderohe in a vault to ensure that he won't be killed by the snarling Zombie King. In another film, Dieter's fate may indeed seem obvious. However, Zeus isn't a typical zombie in Army of the Dead, but rather one that analyzes the bigger picture.
Logic suggests that Zeus kills Dieter in Army of the Dead, but the film clearly shows that Zeus is willing to leave prisoners alive. In this case, it's possible the Zombie King eliminates the German safe cracker, if only because Martin (Garret Dillahunt) previously beheaded the Zombie Queen (Athena Perample). Based on the intelligence that Zeus displays all throughout Army of the Dead, he may actually view Dieter as an asset rather than a convenient snack. Before Scott Ward (Dave Bautista) and company enter The Olympus, they learn that the Alphas won't necessarily attack unless they perceive an immediate threat. When the Queen loses her head (and her baby), that changes the scenario, of course. It's also worth noting that Dieter is the main protagonist of the prequel Army of Thieves, so it makes sense that he would be part of a proper trilogy. By not showing the character's death, Army of the Dead teases his likely return, either as a human or as an Alpha.
In Army of the Dead, Human Dieter or Zombie Dieter likely survived the climactic destruction of Sin City. Since the character is so charismatic and likable, the filmmakers' would theoretically keep him alive for Army of the Dead 2, the third franchise installment. Then again, Dieter's personality traits as a human would make his potential turn as an Alpha Zombie even more jarring. Regardless of the character's fate in Army of the Dead, it's highly probable that he's roaming somewhere around the basement at The Olympus, since it's possible he could've survived if he wasn't outside.
Clues to Dieter's fate can be found in the character's dialogue. At the 91-minute mark in Army of the Dead, he gazes at The Olympus vault and makes a cryptic remark to Vanderohe: "If I can open it, it will be either destruction or renewal... death or rebirth." This line is especially important because it can be used to support conflicting theories. For example, Dieter's death via Zeus would be a "destruction" and then lead to a zombie "renewal," while his potential survival would be a "rebirth," and maybe even as entirely different type of human being in a future Netflix movie. Because Dieter says these words directly to Vanderohe (who survives the blast), it seems like they'll come into play in the sequel. It's even possible that Dieter and Vanderohe could lead a zombie revolution.