He imprisoned his father, likely for over 20 years, killed his wife (though in self-defense), shot his grandson, and frequently resorts to kidnapping and physical intimidation. Both Kazuya and Lee, Heihachi's adopted son, bitterly resent him, suggesting he was also cruel to them in their childhood. Heihachi has an insatiable desire for power, which has included plans for world domination, enhancing his own power through genetic experimentation, and trying to attain eternal youth for himself. He has fought against all of his relatives for his own personal gain. Most noticeable among these are when he seized the family company from his father and later imprisoned him under the family temple, shot his grandson after using him to lure out Ogre, whom Heihachi wished to experiment on to gain eternal youth and power, and when he attempted to capture Kazuya and Jin for use in a Devil-Human Integration Program, that would try and bond human and devil cells. In his personal quest for power, he has progressively led the Mishima Zaibatsu down darker and more sinister routes, militarizing it after Tekken 2 with the creation of Tekken Force, using corrupt business practices, and conducting cruel experiments in the name of expanding the corporation's power. Heihachi is exceptionally good at presenting himself well to the public at large and building the Zaibatsu's public image into a face that hides its darker operations.

Whilst his Tekken Force were searching for Ogre for use in his experiments, for example, Heihachi also had them resolving disputes and cultivating wastelands in order to feed poorer countries, so that he could garner the support of world leaders.

One of the first things he did when retaking control of the Zaibatsu from Jin in Tekken 7 was to try and bolster its ruined image and to try and bring down Kazuya by destroying his image. This manipulation of appearances has consistently been an important weapon in Heihachi's arsenal, particularly since Kazuya, often his main opponent, is not good at presenting himself well publicly.

Heihachi tekken 3 theme