One has to admire how Doomsday rolls. If we were genetically engineered to be murdered repeatedly, in an attempt to become immune to death and destruction, just so we could kill Superman, then we would phone it in for the rest of our days, too.
It's not like he has anything left to prove, it's not like Lex Luthor and company can give him a whole lot of static. All he has to do is ask the room to raise their hands if you've killed a superhero and count his as the only one showing.
The character arguably peaked way too early in his villainous career, and hasn't done anything as epic since, hence his ranking here at number 46. He delivered a devastating blow to DC's most iconic hero, in one of the most well-known comics of all time. But the powers at be have yet to drop him in a story as memorable or worthwhile as the Death of Superman arc.
Despite his crowning achievement coming at the beginning of his infamous career, attention must be paid to this miracle of evolution. He can adapt to anything that comes at him in the field, from sound guns to plasma swords. The more others try to stop him the more unstoppable he becomes (Darkseid and his Omega Beams learned that one the hard way). He does not eat or sleep and his body is made out of bone protrusions he can use as weapons. On the surface, he may seem like a one-trick pony. But we wouldn't recommend saying that to the face of the thing that murdered the Last Son of Krypton.