Apparently, there’s a secret ending in the game with some vey specific unlock requirements. We know about this the way we usually know about this kind of thing: datamining,
as first reported by Kotaku. Some intrepid explorers found what appears to be an ending revolving around disarmament, since removed from Youtube. Here’s the operating theory, based on what you could see in the video while it was still up: there are nukes in the game, which you can use in the multiplayer mode, and the ending will only trigger when there are no nukes left in the game, anywhere. So it’s going to require cooperation on the level that video game players aren’t always known for: it makes “Twitch plays Dark Souls” look like child’s play.
There are, of course, players trying to go about disarming the world’s nukes, calling themselves “Metal Gear Philanthropists” on reddit. They’ve got leaderboards, guides, and everything else the anti-nuclear Snake might need to start breaking into other people’s bases and getting rid of nukes. It’s a Sisyphean task, to be sure: people can always build more nukes.
We’ll keep an eye on the situation and see if the world ever gets close to unlocking this particular achievement, but my guess is that it will take a very, very long tim. You still have to hand it to Kojiima, however: it’s the sort of madness that truly captures the particular messaging of the series. The thing is, it’s either a message about the impossibility of nuclear disarmament, or a message about the true power of cooperation in the service of a better world, and it’s up to the players which one it becomes. It’s the sort of thing that’s truly only possible in a video game, which I think we should always be looking out for.
/SPOILER]
Metal Gear Solid 5's Biggest Secret Is Totally Insane