Complex sentence: He was introduced in the original "Metal Gear" series first as the commanding officer then arch-nemesis of the player character Solid Snake and has later become the protagonist of "Metal Gear Solid" prequels where he is depicted as an American covert operative.
Split into simpler sentences: He was introduced in the original "Metal Gear" series first as the commanding officer and then arch-nemesis of the player character Solid Snake. Later, he has become the protagonist of "Metal Gear Solid" prequels where he is depicted as an American covert operative.