So Metal gear solid 2 he was still human... Metal gear solid 4 he was already cyborg with white blood... Metal gear solid Rising hes a cyborg with red blood, loses limbs and an eye... jaw is also cyborg like...
The Patriots, here's the whole backstory of what happened between MGS2 and 4 with Raiden's terrifying transformation highlighted in bold if that's all you were really looking for.
Raiden and Rose began living together. At some point, Raiden, in large part because of his having to utilize a HF blade weapon late in the Big Shell Incident, became fascinated with the art of Japanese swordsmanship, training himself with the HF Blade and studying in various Japanese swordsmanship and the samurai code, and even going as far as to watch samurai movies. In addition, largely because of his encounter with the Patriots AIs late into his mission, he also did extensive research on the subject of AIs, and wondered whether the Patriots AIs were actually sentient, or simply programmed to be that way. Despite the loving relationship between him and Rose, the tragic memories of his days as a child soldier started to resurface, causing tension in their relationship. He began drinking heavily, getting into fights and eventually decided to leave her. In addition, he was also led to believe that his child had died from a miscarriage.
Raiden learned from Big Mama,in exchange for the location of Big Boss that he obtained from GW, that Olga's daughter, Sunny,was being held in Area 51,and successfully rescued her with the help of Big Mama and the Paradise Lost Army. It was during his rescue of Sunny that he met the former Soviet soldier Boris Vyacheslavovich Popov,who was the war buddy of Sunny's grandfather, Sergei Gurlukovich,who aided him out of the realization that the Patriots were a threat to the world, not just America. After hearing of Rose's miscarriage and subsequent marriage to Roy Campbell,Raiden became despondent. He left Sunny in the care of Otacon and Snake anonymously. Afterwards, he left to wander the Earth. Raiden studied scouting techniques under a Native American shaman living in Alaska, and learned to hunt. He then began work on retrieving Big Boss' remains from the Patriots for the Paradise Lost Army, leading to his capture. 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.
With the help of the Paradise Lost Army, Raiden managed to escape his captivity. After undergoing surgery to clear his body of nanomachines and being saved by Dr. Drago Pettrovich Madnar,he was successful in reclaiming Big Boss' remains from the Patriots. The enhancements implanted throughout Raiden's body, however, were too severe to allow him to live a normal life again. He chose to disappear from the life of his fiancée.
It'd be ideal sources material for a good death metal tune lol