Spock/Alternate realities/Neutral Zone incursion

In an alternate timeline where Captain Christopher Pike avoided his crippling fate, Spock was his first officer on the in 2266 during the Neutral Zone Incursion. Having been brought from 2259 by his future self to see the consequences of his actions, Pike enlisted Spock's help to make sense of his presence in the future and what he was meant to do there. During the following confrontation with the Romulans, Spock worked on repairing the weapons systems on the Enterprise and was severely injured, leaving him in a state similar to the Pike of the correct timeline. Spock's prognosis was grim and even if he survived, he was unlikely to ever be the same again. As a result, Spock could not take part in causing reunification between the Vulcans and Romulans and Pike came to believe that he had exchanged his own fate for Spock's. ()
After showing his 2259 self the future, the Christopher Pike of the alternate timeline revealed that he had learned from the Boreth monks that in every timeline where Pike changed his own fate, Spock died as a result. Because of this, in all of those futures, Spock couldn't go on to do the great things that he was meant to do which would change the fate of the galaxy. ()