McKinless played the role of Ares - one of the mythical Greek Gods of the DC universe - in the film
Justice League (2017). Director
Zack Snyder demanded McKinless sport 'veins like worms and paper thin skin' so it required a very different kind of training for McKinless than what he was used to. After years of athletic and strength based training, McKinless had to quickly learn a lot about bodybuilding and body-composition training in a short duration, which he did on his own without any assistance from a trainer or coach. McKinless admitted that while his ultra-vascular and hyper-shredded look "wasn't particularly healthy", it was the goal he set for himself and achieved it with great difficulty and dedication eventually reaching 6% body-fat and 220 pounds of muscle mass.
He followed a super-strict diet and punishing workout routine which included over 40 cans of tuna per week. He started with a month of very strict dieting, followed by a month of dropping all carbs and a few weeks before filming began, he dropped to a daily intake of between 1200-1500 calories to achieve the balance between maintaining his muscle mass while still burning fat. He was also doing 40 kilometers (25 miles) of cardio per week (both High Intensity Interval Training as well as steady state cardio) to dramatically drop his body fat level and intensify his muscle definition.
In the finished film, McKinless height was digitally enhanced to tower over the rest of the characters and his voice and face were replaced with that of actor
David Thewlis who also portrayed Ares in
Wonder Woman (2017). McKinless has said that he will probably never get so lean again as he did for this film and that it was a great honor to play this role.
