Heihachi is the Mishima with by far the strongest mids and pokes, which come with the tradeoff of an underwhelming set of lows. With great frames but not much to do with them, he's often attacking a lot more than his opponent.
He has an extensive suite of noob killer moves which have to be answered by fuzzy guards or reacting, and his f,F+2 is notoriously difficult to punish due to its pushback. On top of all this, his f+4 is the best bully move in the game, demanding patient defense to escape the pressure.
Insane neutral with both an electric and tonnes of strong mids