Don't crank up the difficulty if it isn't warranted. First, it's arbitrary and second, it would cheapen the really bad stuff. You just have to bring in some really bad stuff first;
Guy shot by a gangbanger? Not much of an issue. (3 difficulty)
Guy disemboweled by a ghoul or burned to death by a wizard? Disquieting. (4-5 difficulty)
Guy eaten alive by a nasty fiend, kicking and screaming all the time? Scary. (5-6 difficulty)
Guy drained by a black court, his humanity/soul rotting away as he's turned into an undead? Terrifying. (7-8 difficulty)
Guy tortured by a Naagloshi, mind shattered, soul eaten to add to the thing's power? Nightmare fuel. (9-10 difficulty)
Guy touched by an Outsider from the Void, his mind, soul and entire existence perverted and subsumed by an Emptiness too vast to imagine that seeks to consume all of Creation and has destroyed countless civilizations, that just gained a foothold in this world by the murder? I'm in ur skull eatin' your thoughtz. (12 difficulty)
And once he gets a consequence via The Sight, especially if it is something really nasty, you can tag the consequence for effect once for each scene it remains for him to have another, more limited attack. The more limited attack isn't going to inflict more consequences but it might inflict stress... and having that sort of nastiness stuck to his head again and again will hammer in the point that what The Sight reveals is there to stay.
Plus, if seeing the murder done by something sufficiently nasty like a Naagloshi or Outsider psychically wounds him like that, the player will realize that keeping The Sight open against a shapeshifting or posessing enemy might mean his character gets to see through the enemy's human mask the first time they randomly meet. Which might be bad.