WARNING: The following contains major spoilers for Sinister War #3, available now from Marvel.
In Marvel's Sinister War, Kindred brought in every Spider-Man villain imaginable to go into battle with the wall-crawler. Fom the Sinister Six to the Savage Six and everyone in between, a myriad of villains is out to kill Spider-Man. Powered by Kindred's dark designs, their goal was to win this war and save their souls from the damnation that Kindred promised those who fail.
The demon has also brought several villains back from the dead, including Mysterio and Sin-Eater. While Mysterio believed his part finished and tried to move on and Sin-Eater took his own life when he learned Kindred was not what he believed, the villain hadn’t finished with either of them. In Sinister War #3 by Nick Spencer, Ed Brisson, Mark Bagley, Carlos Gomez, Ze Carlos, Andrew Hennessy, Andy Owens, John Dell, Brian Reber, Andrew Crossley and VC’s Joe Caramagna, Kindred wouldn’t let Sin-Eater off that easily and resurrected him again.
In Amazing Spider-Man #54 by Nick Spencer, Matthew Rosenberg, Federico Vicentini, Takeshi Miyazawa, Scott Hanna, Erick Arciniega and VC’s Ariana Maher, Sin-Eater lures Spider-Man into a trap that Madame Web helped him fight. She let Sin-Eater take her sins, but that allowed him to see the truth about Kindred, and he realized the demon had lied to him. The truth of what was really happening caused the villain to turn his gun on himself. He ended his role in Kindred’s plan on his own terms. However, Kindred wouldn’t allow that.
Kindred brought Mysterio back from the dead to start his plans. Quentin Beck took his own life before this, which might play into how Kindred has his claws in him. Sin-Eater did the same, and now Kindred brought him back from the grave, literally, to add to the army trying to kill Spider-Man. With the wall-crawler getting beaten badly, Kindred pulled out the last part of his plan -- what he called the “final players” in the Sinister War. He brought villains from their cells, their hiding spots, and their graves, the last man being Sin-Eater.
This wasn’t the same Sin-Eater that Spider-Man fought just a short time ago. This was Sin-Eater with a deformed face, rotted from his death place, and he wasn’t alone. Now, Spider-Man has to fight even more villains than the Sinister bad guys. What makes Sin-Eater such an interesting villain to return for the last battle is that he hates both Spider-Man and Kindred. With that in mind, Kindred had no problem bringing him back from the dead again, saying he might hate Kindred, but “I don’t think that will stop him.”
Sin-Eater proved when he helped Kindred start his war with Spider-Man that he was nothing if not a zealot. He wreaked havoc along the way, stealing powers from everyone from Green Goblin to Juggernaut to Morlun. It took the entire Order of the Web to stop him, and now he is back from the dead again and ready to begin Kindred’s ultimate act in the war, where he tries to prove that nothing Spider-Man does will change his fate