The sight of Tails' gruesome corpse, with bloody gashes all over even in the eye, in issue 3. Overlaps with Tear Jerker, because of how much Sonic misses him and regrets not being able to save him.
Nicole making Metal Sonic attack Vennie in issue 8. The sight of her, pictured to the right, lying on the ground unconscious with her eyes still open and blood leaking out of her body and mouth is gruesome.
In issue 9, we see Metal Sonic with large stains of Vennie's crimson blood on him.
Yo Vennie Erin, she was just 14 When her sister built a very strange machine It was designed to fight blue blurs, unseen When the machine didn’t work, her sister just quit But then Vennie took a look inside of it There was a red eye's flash, a metal claw in range Her intestines got all rearranged!
The way Scourge's spirit decays whenever he gets weaker. The first time he appears in issue 10, he's basically a skeletal zombie.
A more slow burn example, but Nicole creepily assures Sonic in issue 9 that the soul is just a myth, stating that a "ChaosSpirit" is just a copy of the original body's consciousness and nervous system. The scary part is Word of God confirming that she is right. All of the Ghosts wandering around? Tikal? Sonic? Vennie? Just copies who will eventually become husks of themselves before dissapearing. Then, depending on your interpretation, he either gets copied into Metal Sonic or he becomes Metal Sonic while a copy just pops up in his original place. Luckily, this is Sonic, so he doesn't really look like he cares, but damn.