What-If: Spike wakes up one day and finds that his friends, the Mane Six, have mysteriously vanished? What will become of Equestria without six of its greatest heroes? Can Spike be the hero everyone need? And will he find his missing friends?

The general synopsis is:

Spike experiences a bad case of imposter syndrome (or maybe inferiority complex) when he started comparing himself to his friends, the Mane Six. He came to the false conclusion that he's not a hero and that the Mane Six can manage without him.

The next morning, however, Spike discovers that his friends have gone missing and Equestria is in disarray, with too many friendship problems by the days, and bad guys running loose. So it's up for Spike to search for clues to find his missing friends, where they are, and send the bad guys to prison. But on the way, he finds himself and discovers the hero he truly is inside.

7959011
Neat. Yeah he learned being a Princess isn’t easy and here he learns being a hero isn’t any easier

7959018
He may be a big shot in the Crystal Empire, but Spike will eventually learn that being a hero for Equestria, and the world, is another level.

7959011
Yeah. Definitely sounds like it could be an intriguing one if the right person were tackling it. Kind of like Mystery Incorporated finding out that having a better track record against the Joker than pretty much any other hero that's NOT a member of the Bat-Family is one thing - straight up having to fill in for the Justice League is another matter entirely.