Doctor Doomsday is a character in the Amalgam universe. He is an amalgam of Marvel's Doctor Doom and DC's Doomsday.
In the Amalgam Universe, Victor von Doom worked with Reed 'Prof' Richards, Sue 'Ace' Storm, Johnny 'Red' Storm, and Ben 'Rocky' Grimm in some sort of space program. It was these four who actually went into space, while Victor remained behind and manned the operation from headquarters. During this time, however, Victor became jealous of the fame that he believed that the four would receive upon their return. Therefore he sabotaged their mission, causing them to drop back towards the Earth. The four, however, survived the crash. From that day forward, they called themselves the Challengers of the Fantastic.
Later Victor became suffused with the DNA of an alien creature (probably one much akin to DC's Doomsday, if not Doomsday himself), perhaps in a lab accident. He then ran off to the Balkan nation of Latkovia, where he became known as Doctor Doomsday, a genius in the body of a practically indestructible monster.
When Galactiac came to Earth, it caught the attention of Dr. Doomsday, who quickly whipped up a plan to steal the power of the Silver Racer. He was successful, but it is unknown how events followed, assumingly he would have suffered a defeat at the hands of the Challengers of the Fantastic.
Doctor Doomsday is noted as being one of the most powerful villains in the Amalgam Universe. He is also noted for working with Thanoseid.
Doctor Doomsday's abilities include a combination of both Doctor Doom's and Doomsday.