That wasn't the real Pinhead in this
If you want the true Pinhead go and watch the 1st and 2nd films. They tried too hard to make him like someone like Freddy Krueger in this one. In the first 2 films he was a very calm and menacing figure who would even make deals with Kirsty and let her go. In this he just went around on a killing spree for no reason killing anyone he came across and laughing like Freddy after every kill.
Wasn't it he only killed those who opened the box looking for pain and pleasure? I mean he let Tiffany go in Hellbound after she opened the box because she wasn't the one who desired it. In this film he's nothing more than a Freddy/Jason figure jut killing anyone, his mystique and presence is completely gone in this film.
Also his voice was too regular in this, it didn't have that godly demonic tone it had in the previous films.
When Gotham is ashes... you have my permission to die. -Bane