The Doomsday Clones is a series of genetically engineered clones created from the savage intergalactic serial killer Doomsday and villains in the DC comics.
One of the Doomsday Clones boss in the video-game, Justice League Heroes - he is based physically on the Doomsday found in the Animated DC universe but is more intelligent than most incarnations of the beast, being capable of speech and higher-functioning plans.
The Doomsday Clone infiltrated the Justice League Headquarters with the aid of Brainiac and attacked a lone Martian Manhunter while the others were occupied with a White Martian invasion and a Gorilla Grodd assault (all orchestrated by Brainiac).
After the heroes fought through their own security-system they were confronted with the Doomsday Clone, who also had the aid of Minor Clones, which were smaller versions of himself.
The Doomsday Clone was too powerful for the heroes to defeat by traditional means, so they had to use a powerful laser-weapon to weaken the monster sufficiently for them to defeat him.
The Doomsday Clone had superhuman strength, invulnerability and the ability to create shock-waves either through his strength or energy-manipulation.