For Mission: Impossible - Fallout, his sixth cinematic adventure, the biggest challenge that stood in Ethan Hunt's way was August Walker, played by Henry Cavill. While August will arguably be best remembered for his movie-sabotaging mustache, he did prove himself to be a dangerous adversary for Tom Cruise's character, but that element of his character was established by director and writer Christopher McQuarrie in the middle of principal photography. As Cavill recently told CinemaBlend:
The biggest change I would say was the threat level of Walker. He began as more of a thorn in the side of Hunt and ultimately became a formidable opponent with a driving story by the time McQ was done with him.
Having enjoyed a successful run in theaters this past summer, Mission: Impossible - Fallout is now finally arriving on home media, and CinemaBlend's own Eric Eisenberg had the opportunity to speak with Henry Cavill about his time on the movie. Regarding how the finalized August Walker differed from how he was initially conceived, Cavill explained that August actually became more dangerous to Ethan Hunt as filming progressed, resulting in him becoming one of Ethan's greatest enemies.
While Mission: Impossible - Fallout's marketing did its best to hide August Walker's true allegiances, it certainly did a good job of setting him up as someone useful in a fight. One of the best examples of this is the bathroom fight at the Paris nightclub, where Ethan Hunt, while distrustful of August, still believed they were on the same side and worked with him to take down the man they thought was John Lark. Alas, how wrong Ethan was thinking that August was one of the good guys.
For the first half of Mission: Impossible - Fallout, the true identity of IMF's target, John Lark, remained a mystery, and August Walker was simply the Special Activities Division operative that CIA director Erica Sloane sent to shadow Ethan Hunt and help retrieve the stolen plutonium. But eventually, following a failed attempt to frame Ethan as Lark, August was revealed to be the real Lark, and he helped Solomon Lane, the main antagonist from Mission: Impossible - Rogue Nation, escape custody.
While the bathroom fight was cool to watch, it was in Mission: Impossible - Fallout's climax that August Walker arguably best demonstrated how formidable he was, avoiding Ethan Hunt on helicopter for a while and then throwing down in fisticuffs on top of a snowy mountain with this franchise's main protagonist. August nearly managed to outlast Ethan but in the end, he got what was coming to him: a hook-line to the face and his body being incinerated in a helicopter explosion. The villain was defeated, Solomon was handed over to MI6 and the one-third of the world's water supply wasn't contaminated by radiation. Ya, victory!