Any fan of comics and genre movies know that good guys and bad guys periodically switch sides for convoluted reasons. It makes being a judge or juror in these worlds a confusing and somewhat comical endeavor. Let’s look at the most common causes for this behavior and see how you pass judgment.
In the first X-Men film, Charles Xavier takes control of Sabretooth and forces him to grab a hold of Magneto’s neck. This is a perfect example of one entity taking total control over the body of another, or body hijacking. The one who lost control need not take any responsibility for the actions they appear to take because the actions are actually taken by someone else. Blaming Sabertooth for choking Magneto would be like blaming a gun owner whose gun was stolen for the crimes the thief later uses the gun to commit. Even so, the noblest heroes often feel terrible for the damage their bodies caused while hijacked and some try to take precautions to limit such a transgression. Superman, knowing body hijacking is possible in the DC Universe, gave Batman a kryptonite ring. Not a bad plan.
Speaking of Superman, the nefarious Maxwell Lord once used his mental abilities to make him see Wonder Woman as Doomsday. Superman fought Diana ruthlessly as a result. Mysterio used special effects and drugs on Wolverine to trick Logan into thinking his fellow X-Men were invading villains. Trickery like this can make almost anyone do almost anything, but it doesn’t take agency away from the perpetrator the same way moral hijacking does. Both Superman and Wolverine have some small responsibility for their actions, in this case. After all, a dogmatic adherence to never taking a life would still keep a hero from killing regardless of who they think they see before them.
Marvel’s ‘Secret Empire’ features Captain America as a Hydra agent. Yes, the Hydra that was affiliated with the Nazis. The story is still playing out so it’s not out of the realm of possibilities that Steve Rogers is a victim of mind hijacking or illusion or something worse, but as it stands now, it seems as though Cap is a Hydra agent because he actually believes Hydra philosophy. A reality-manipulating girl may have retroactively indoctrinated this into Cap, but that may also be beside the point. Since that plot is still in progress, let’s continue with one that is complete. In ‘Superman/Batman: Absolute Power’, time-traveling villains go back in time to raise Clark Kent and Bruce Wayne as their own. The villains teach the boys to grow up into dictators willing to kill to maintain power. Indoctrination into cults and terror organizations exists in the real world, and the moral culpability in those cases may be questioned, but when a life is engineered through time traveling trial and error to output an adult with a very specific ideology? How should blame be distributed then when that ideology creates a monster?
In the real world, people are peer-pressured into immoral actions and that rarely gets them off the hook. In sci-fi and fantasy, the pressure is a bit more substantial. Take Green Lantern Hal Jordan, for instance. A magic alien parasite once bonded with him, which resulted in Hal killing a bunch of people, debatably the entire universe. This is similar to the alien symbiote Venom coloring the actions of Peter Parker, Eddie Brock, or whoever it uses as a host. Hal and Peter are still at the controls and acting according to their own motivations, but an external force is giving the devil on their shoulder a loudspeaker.
The most famous examples of this come from the most famous fantasy and sci-fi series of all time. In the ‘Lord of the Rings,’ being near the one ring brings out negative emotions. In ‘Star Wars,’ the dark side of the Force corrupts with its power. The Force is unique from the rest in that it takes any momentum a person has, good or evil, and supercharges it. Considering this, does Anakin deserve more or less blame than a common stormtrooper?
So as you can see, just because someone is deemed the good guy, it doesn’t mean that they are immune to commit evil acts. Despite the reasons for those actions should they still be culpable? You be the judge.