Tekken 8 finally gives fans a definitive answer about whether or not Kazuya is actually evil or if he's being controlled and influenced by the devil gene.
Although Kazuya Mishima started off the Tekken series as one of its main protagonists who was just out to get revenge against his father, Heihachi, he quickly turned into an even more evil and villainous character. For the longest time, fans have wondered if this personality switch is due to the devil gene within him, or if he's just plain bad to the bone, something that Tekken 8 finally definitively answers.
Ever since Kazuya was revived from death in Tekken 4, it's been hinted that his devil side has completely taken over him and that any good that was there has been completely removed. This brings about an interesting question - if Kazuya didn't have the devil gene, would he stop trying to take over the world and be a more heroic figure?
Spoilers for Tekken 8’s story follow.
The final two chapters of Tekken 8 finally clear this mystery up once and for all, as Jin and Kazuya fight in their Devil and Angel forms respectively and end up getting rid of the power altogether. This doesn't stop Kazuya from trying to kill his son, however, which certainly seems to indicate that he's still evil.
Kazuya's ending in Tekken 2 implied that he was having an internal battle with his devil side, which caused many fans to think that he had been taken over by it and wasn't actually evil of his own accord.
As pointed out by Redditor pinkpugita, Kazuya actually answers the question himself when talking to Jin after his Devil powers are gone, saying, "So what? It's just a means to my goals". This is taken even further if you let Kazuya win against Jin in the final battle, which unlocks an alternate bad ending.
In this ending, Kazuya, without his Devil gene taking him over, defeats Jin and then chooses to seemingly kill him by chucking him off a cliff and onto some rocks that would certainly kill most people. Even if Jin did
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