Creator: DC Comics
Debut: 1992

The monster that took down the entire Justice League before killing Superman definitely deserves to be on this list. What still stands out, so many years later, is how Doomsday made the Son of Krypton hurt. After decades of watching Superman come out of conflict after conflict alive, with nothing but a ripped cape to show for it, we finally saw his skin rip, tear, and bleed profusely. 

Add to this Doomsday’s incredible resistance—he would become resistant and immune to anything that had previously “killed” him—and you have one tough customer. He didn’t have much of a personality beyond blind rage, but that one-tracked mind made him even more terrifying.