Worst yet is Johnny cacklinginsanely in the midst of his agonizing screams. Word of God said it's the Rider himself laughing with glee at finally being unleashed.
His dispatching of the three elemental demons, complete with them screaming.
The first time The Rider uses Penance Stare.
Every time he says LOOK INTO MY EYES.
The effects of the Penance Stare are pretty horrifying. The victim gets a replay of all the suffering they've brought upon others, all at once, peppered with screaming, warped, demonic faces and skulls. All in lovely, flame-filled Hell Vision.
Blackheart's occasional transitions into his devil form are a bit cheesy, but Mephisto's subtle morphing can make you shiver.
Every time Blackheart kills someone. He literally drains the life from them, causing their facial features to distort, their skin to turn blue, and black veins to etch themselves across the victim's skin (leaving them with an appearance not unlike Samara's victims in The Ring).
The scene where Blackheart shows up in Johnny's loft:
Roxanne: Jesus!
Blackheart: Not even close.
(Roxanne turns to see Mack — Johnny's pit crew leader and best friend — standing frozen in place. His skin turns blue, his eyes sink back in their sockets, and his lifeless body collapses to the ground, revealing Blackheart.)
Johnny turns into the Ghost Rider. One Youtube commenter described it as "what happens when super saiyan goes wrong".