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The Moment of Truth is a GTA 5 Secret Achievement. It is an achievement/trophy that you can easily acquire while playing the games campaign normally.
To get this achievement/trophy, the mission Bury the Hatchet needs to be completed.
(There have been reports that the achievement/trophy sometimes glitches and doesn't unlock the first time if you play the beginning as Trevor. I suggest playing as Michael to be safe.)
Once the mission is complete (Trevor lands the plane after speaking to the triad leader), you should be awarded with the achievement/trophy.