Real Ending Explanation [SPOILERS] (Metal Gear Solid 5: The Phantom Pain)

In the end, Big Boss (the real one) rides off on a bike. After that, we are shown Venom Snake (Medic from GZ), who examines himself in the mirror and then turns on the tape, where the real Boss says: "Like, thanks, buddy, you saved me from death, but you created your own legend." Then the Medic takes a cassette out of the player and inserts it into another player and sounds of interference are heard. * Moving on to the moment that interests me. * Then the Medic looks at himself in the mirror again and, we see in the reflection of the "Demonic" Snake (a huge horn-splinter in the head, and he himself is covered in blood). He breaks the glass and we see a normal Snake again. Question: It turns out that Snake has become bad, or, on the contrary, he breaks the glass, and thereby "kills the demon in himself"?
The moment starts at 8.21