As much as I hate to say it, and I really do, Jin has a shot.
yeah he does. i dont hate jin so i don't mind saying it though.
You're right that Kazuya wasn't devil, but Jin wasn't fully transformed either. If he could quickly KO Heihachi, he could take Kazuya then return to kill Heihachi since this is to the death.
well there is a whole thing with devil powers that needs to be clarified. i've done it in great detail on my site but i'll summarize it here:
-devil's power is kazuya's power. they are basically two different personalities living off that one power.
-the only difference is that when Kazuya transforms to devil (or when devil takes over) he simply gets the ability to fly, shoot beams from his third eye and get other powers like telekinesis etc. Basically Kazuya is the half-way of that power because while he draws of it during combat, unless he turns to Devil he can't completely manifest that power and give it a proper outlet.
-at the same time, kaz and devil are two seperate entities fighting for control over the same body and power source. either time the other is vulnerable, the dormant personaility takes over (kaz takes over devil in his T4 ending when devil was shocked that he cant merge with jin....and in the same way devil takes over kazuya in his T5 ending where a vulnerable kazuya with Jinpachi suddenly turns to devil........anytime kaz's voice is doubled and his eye or both eyes glow brightly then its Devil talking as the dormant personality)
-the fact that Kazuya's left eye is red in T4 onwards is basically a sign that Devil powers are active in him. when they are not active and he isn't relying on that power both his eyes remain brown.
-the same applies to Jin only in his case, carrying the angel/kazama AND devil powers at the same time makes him volatile and unfocused. notice that prior to T5 he never completely gave into it so he never completely transformed. that changed with T5 because Jinpaci's awakening made him lose control completely. result=emo jin.
so what happened in T4. well basically, for one notice that kazuya locked away Devil in himself. he put him into submission and hid him away and both his eyes became brown. that means that he was only at his base level human power (being a mishima its still insane). he needed to look away Devil so he could get the devil part out of jin and into himself without having the kazama blood prevent it like it was with Devil. basically, kazuya intended to "sucker" the kazama blood in jin because the kazama/angel blood is a direct counterpart of devil (asuka unconsciously purged devil in jin and jin's blood unconsciously prevented devil from taking his powers).
what went wrong was that kazuya greatly underestimated Jin in thinking that he could take him on without using devil powers (he's always been a cocky, overconfident SOB). Jin was accessing his devil powers and has been since he got branded by devil prior to T3. on top of that he was already pissed off in T4 and had already party transformed into Devil Jin (the tattoos etc). basically it was shitepissed Jin using his devil powers and rage against an overconfident Kazuya at base human strength.................the result absolute pwnage to Kazuya. after that, when Hachi showed up, Jin got even more pissed and practically turned into Devil Jin.
~Sado