(Even though the movie was released in 1996, I will hereby provide a SPOILER WARNING for those of you have not seen it yet and do not want a key plot point revealed. So turn away now or continue reading at your own risk.)
The main villain of the first Mission: Impossible movie was the character Jim Phelps. Yes, they turned the noble hero of the television series, played so well by Peter Graves for many seasons (including appearances in the short-lived 1990 TV remake), into the bad guy. In the movie, Jon Voight played the part of Phelps, who has become a bitter murderer now that the Cold War is over.
Turning Phelps, the leader of the covert team (who came to the rescue of America and the world during countless adventures) into a cold-blooded traitor was a slap in the face to fans of the original series. The filmmakers were trying to be clever, but instead they negated the heroic legacy of the classic team. What's next? Will Tom Cruise play a villainous Ethan Hunt in the inevitable Mission: Impossible reboot twenty years from now?
The storytelling gimmick of taking a hero and turning him into a villain may work in professional wrestling and superhero comic books, but it usually doesn't work elsewhere. The problem is continuity and motivation -- usually, the 180-degree turn in ethics goes against everything that has already been established about the character up until that point. Why would the character then change so dramatically?
Goody-two-shoes heroes have often been replaced with more edgy anti-heroes that have more realistic chips in their armor, making them appear more human, but turning them into completely amoral killers is a step too far.
Thank goodness we still have the original Mission: Impossible episodes starring Peter Graves to remind us what real (fictional) action heroes can be.