Really? The same man who threw his own son off of a cliff when he was 5 years old (& making him very warped as a result), then threw him into a volcano at the end of Tekken 2, tried killing his own grandson at the end of Tekken 3, & has his own father imprisoned underneath a compound, while also letting him starve to death?
You have to be kidding me. If you ask me, Heihachi is the evilest of the bunch.
At the end of the day, Heihachi is the human kind of evil. He wants to rule us, not to destroy us which is what Kazuya (aka Satan incarnate) wishes for.
Let's look at the evidence
- When Heihachi was in charge of the Zaibatsu during the T2-T3 interim, he ended world wars and stopped world hunger. Granted, it was to build a reputation but like Elsa from AHS: Freakshow, some good came out of it.
- When Jin and Kazuya were in charge of the Zaibatsu, they started wars (For Jin, it was to summon Azazel, for Kazuya it was for lulz)
- All instances of Heihachi throwing people off cliffs/volcanoes/outer space were done with people who were in possession of the Devil Gene. Need I remind you these people's powers have been CANONICALLY stated to be evil?
- Heihachi has shown the capacity to love. Kazumi says Heihachi still loves her and he apparently has fondness for Kuma 1 and 2. Kazuya hasn't loved anyone in his life.
- Heihachi rescues Kazuya from Devil's beam in his Tekken 2 ending, Kazuya responds by using him as a human shield
- Heihachi is often seen in comedic endings, no such treatment is given to Kazuya
- Heihachi is a hero unit who joins the good guys in both crossover games (Namco x Capcom and Project X Zone), conversely Kazuya is always with the villains.