Raiden is the only Cyborg Ninja in the series to survive the events of the game in which he is featured. He is also the only Ninja to have never fought Solid Snake in a main game, either during gameplay (Gray Fox) or off-screen (Olga Gurlukovich).

Was Raiden always a cyborg?

As a prisoner, the Patriots used Raiden as a test subject for experiments in exoskeletal enhancement surgery, during which he had his head and spine excised from his body from his lower jaw down and subsequently grafted into an enhanced synthetic body. It clearly states he had no choice in becoming a cyborg.

How much cyborg is Raiden?

The body, merely titled "Raiden", is a wearable suit in Metal Gear Survive, and can only be unlocked by purchasing it with 5000 BP.