Metal Gear Solid 3: Snake Eater: ColonelYevgeny Borisovitch Volgin is a Sadist who, within minutes of appearing, fires a Davy Crocket nuke at his countrymen just to give it "a test drive," knowing full well that he won't be blamed for it, even when one of his subordinates is clinging to his arm, begging him not to. Then come one of the most vicious Cold-Blooded Torture scenes in video games. It's clear he didn't care if the torturee lives or dies before getting the proper information, as long as he gets his kicks. Then we also have the fact that Volgin, long before the events of the game, had participated in the Katyn Forest Massacre as a NKVD member, where he managed to kill over 20,000 Polish officers with his bare hands, and not only that, but he also removed their blindfolds before beating them to a pulp, and he killed several people in both the Hungarian Revolution and the East Germany Uprising, which he not only had absolutely no regrets about killing 100,000 anti-communist activists, but even boasted about the feat.
Metal Gear Ac!d2: Wiseman instigated a horrific event known as the Praulia Massacre: Wiseman felt that the data about the Model 2 soldiers was insufficient, so he had technicians provoke said soldiers into going berserk, causing the deaths of 10,000 people. He then sent the Model 3 soldiers in to eliminate the Model 2 soldiers, knowing that eliminating their brethren hurt them. Besides this, Wiseman was also responsible for the death of Koppelthorne's wife, which also resulted in the events of what happened later on. In addition, he had Venus render Snake amnesiac in to help him obtain the Lucinda File with the evidence of the massacre, and had Venus execute him simply because he outlived his usefulness.
Metal Gear Rising: Revengeance: Sundowner is a war profiteer who seeks to spread War for Fun and Profit around the world, believing it to be the natural state of mankind. He begins the game by killing President N'mami in front of Raiden whilst being needlessly sadistic, and has street children kidnapped while their brains (of which we see hundreds) are removed into cyborg casings while they are aware the whole time. They're forced to commit endless atrocities in virtual reality before they are sent off to commit them in the real world as well. Sundowner has no good intentions or vision for peace like Hot Coldman or Revengeance's own Big Bad; he's more sadistically gleeful and sociopathically unrepentant of his atrocities.