So, this question bugged me for quite a while, "why is Azazel an antagonist in the series, like a giant Egyptian crystal monster, kinda weird, especially after Jinpachi as main boss in Tekken 5?" Then it hit me, Jinpachi got his powers FROM AZAZEL! Hear me out here please and you will at least consider it.
FIRST: Their designs - While the two look very different there are some considerable things to be noticed. 1. They both have glowing eyes. In Tekken, glowing eyes are generally associated with power or the devil gene. One example being Ogre for power and Devil for the devil gene. Now with Jinpachi being a mishima, he doesn't have the gene as Kazuya and Jin do, what with Hachijo blood BUT Azazel is said to be the origin of the devil gene, thus Jin's war to awaken Azazel and end the devil gene (kinda failed tho my dude, love ya still) and he has glowing eyes, which Jinpachi also happens to have. 2. They both have giant spikes sticking out of their bodies - couldn't find any symbolism here, sorry. 3. Both have purple skin tones. Much like devil, Jinpachi and Azazel are both purple. And this purple seems to be constantly associated with the devil gene, save for Jin, which could be explained with his Kazama blood and that whole healing touch thing that they have. Even when Kazuya goes Super Saiyan in 7 and kills heihachi (cue evil laugh) he is still purple.
Okay, now that the designs are covered, their abilities. So this may seem like a bit of a stretch seeming as how Jinpachi doesn't fight with beetles and giant crystals but there ARE some similarities. 1. They both have the ability to stun you and BOTH by hitting you with their RIGHT HAND and it's important to note that the position taken by your character is the same in 5 and 6 after being stunned and also, who else can do that? 2. They both have the ability to teleport. While Jinpachi isn't randomly falling from the sky, both he and Azazel do have a move where they teleport back a few feet, avoiding your attack and launching a devastating one in return. 3. This is a stretch but their stronger attacks cannot be blocked, only sidestepped, those being Jinpachis Fireball (my gawd I hate that) and Azazels Laser.
This may be the weakest of my arguments but it's a valid point to be made so feel free to ridicule it as much as you want but here it is, Jinpachi's death, and temples. In The devil within mode in Tekken 5 there is a level which you must navigate which is actually an ancient temple. This is more likely a swing to ogre from Tekken 3 but it's mentioned because Azazel is found in, well, a giant temple and Jinpachi escapes from the Ancient Hon Maru temple after it is blown up. And ogre has a temple for himself too.
Now, putting ogre behind us, the next thing to speak about is Jinpachis death. The first thing to cover is that he is killed by Jin, who also killed Ogre two games earlier and then goes on to kill Azazel in 6. Significances in these are the following. 1. All were killed by Jin, a person with the devil gene AND the Kazama healing touch, giving him hellish powers and cleansing abilities so to speak. And 2. All turned to sand after the were killed by him, although azazel's remains weren't found, it's safe to assume they would have been had they not turned to sand, as Jin had been found and the fact that Azazels Temple crumbled to sand afterwards.
So now all that is out of the way the only question left is HOW DID THIS ALL HAPPEN? And the answer is simple. When Jinpachi was on the brink of death in prison, Azazel, still only a spirit (as Jin had not started the war to fully awaken Azazel) speaks to Jinpachi as he did to Kazuya and Jin. He then possesses his body, providing it with strength and power. Then he escapes, takes the zaibatsu and announces the KoIF5.
That's what probably would've happened but then from this scenario comes one last question. 1. Why didn't Azazel die with Jinpachi when Jin killed him? Another complex sounding question with a relatively simple answer. Azazel didn't die mainly because the "power source", Azazels orb, wasn't destroyed. The orb is the source of Azazels body, his powers and all his evil. Jin awoke Azazels body by causing enough panic and chaos with his war which provided the orb with enough malevolent energy to do so. When Jin kills Azazel, he punches right into his chest, right where the orb is, destroying it and Azazel. If this isn't enough. In Hwoarangs Tekken 6 ending, he pulls out the orb and it rapidly possesses him, turning him purple and demonic only momentarily, before he drops the orb and crushes it under his foot, destroying it and Azazel. (Ganyru also get possessed but let's forget that) and as a final note, in Raven and Dragunovs ending, Azazel still has a physical body because the orb is powering it and Raven realises this, thus his taking of the orb rather than the entire body.
Boom, mind blown. If you read this far, thanks for sticking with it. Reply with your opinion on the matter, have I convinced you? Anyway thanks and just remember, that's just a theory, an hour of my life I'm not getting back! 👍🏼