Terminator Salvation sees Marcus choosing humanity over the machines, giving his heart to save John after he is fatally wounded. The ending, as well as the movie itself, was met with a lukewarm reaction from fans and critics, with the franchise once again switching course away from Terminator Salvation's storyline with the next movie. However, it is possible that the reactions would have been different had Terminator Salvation chosen one of the originally planned endings, either of which would surely have been controversial.

The First Terminator Salvation Alternate Ending Is Bleak

Terminator Salvation Nearly Ended The Human Resistance In A Devastating Way

Terminator Salvation director McG previously teased a darker version of the movie than the one that was released in theaters, and the original ending certainly confirms that. The ending that was planned would have similarly seen John Connor seriously wounded, but in this version, he would ultimately die. The rest of the resistance would then decide to allow the legacy of John to live on by grafting his likeness onto the exoskeleton of Marcus. However, this ended with a devastating reveal that Marcus was indeed working for Skynet. As McG explains (via Gizmodo):

We had a jet-black ending. Connor dies, we’re in a room with all the people we care about. You take Connor’s likeness, you put it on the living machine of Marcus. He sits up, now looking like Christian Bale, takes a gun, kills Kate, kills Kyle, kills Star, kills everybody, eyes flare red, [snaps] the end.

Certainly, it would have been a brutal ending and the bleakest moment in the entire Terminator franchise up to that point. McG seemed to anticipate the reaction fans would have and acknowledged that the shocking ending would have led to some angry audience :

I would hope the oxygen would just go right out. You’d be like, “They can’t do that. That’s the biggest bummer I’ve ever seen in my life.”

It is not hard to see why that ending was not used. The Terminator franchise is a big property, and that ending would have made it very hard to continue on with more movies. However, beyond that, there is the question of what the ending really gives to fans. It would certainly have been a shocking way to end a big blockbuster movie, but there has to be more to an ending than just catching the audience off guard. It certainly feels bolder, but that doesn't mean it was the right choice for this film, and the second alternate ending was a better fit.

Terminator Salvation's Second Alternate Ending Is A Bit More Optimistic

The Change To John Connor Would Have Been Controversial

The second alternate ending of Terminator Salvation would have taken a slightly brighter approach, but would certainly still have been met with controversy. The second ending that was planned would have followed a similar setup as the first one, with John Connor being killed in battle and the resistance choosing to put his skin on Marcus, thus keeping the leader of the resistance "alive" for the people following him.

This time around, Marcus would not have turned on the humans but willingly accepted the role and become the new leader in disguise, as a way to honor John. The ironic twist of the Terminator franchise, leading to a machine leading the human resistance, would have been a very interesting place to go, and could have left the door open for many new directions to head in for sequels. However, the fan backlash to Terminator Salvation's twist ending would have been hard to overcome.