Eric Carlesi's changing hair length during the Val Verde assault scene was kept in the film by Combes as a nod to Samurai Cop, when Matt Hannon was forced to wear a wig for reshoots.
For the English version, all of the actors were dubbed by English-speaking voice actors that Combes sourced from VoiceBunny.com, except Charlotte Poncin, Thyra Hann Phonephet, and Stéphane Asensio. Poncin is fluent in English and works as an English teacher. Phonephet also speaks fluent English and managed to hide his French accent with an exaggerated Vietnamese accent. Asensio recorded his English lines for the pizza delivery scene.
For the French version, John, Hopkins, and Kinsky were dubbed by French YouTubers Ganesh 2 and Superflame to give the film the feel of a French-dubbed American action film. They gave John an Arnold Schwarzenegger voice, Hopkins a Bruce Willis voice, and Kinsky a Christopher Lloyd voice.
In creating this film, Benjamin Combes was inspired by action films from the 1980s, especially American Ninja and Commando. He also drew inspiration from the 2011 film Drive and the 2013 video game Far Cry 3: Blood Dragon.
Combes envisioned Colonel Kinsky as a mashup of every villain from 1980s action films, especially Arius from Commando.