I figured it was about time I threw a bad guy in here and there!
The NuClone is one of the biggest threats that the Guardians of Justice face, as you might imagine from the picture. I came up with him (originally called the "Nukulon," but years later, I thought better of it and changed the name) because I wanted a threat that would be something huge, massive and powerful, where there could be a real concern that he might not be able to be defeated.
The NuClone began his life as part of a research project based just north of the Bellevue, WA area. The facility was, according to what the public knew, researching ways to regrow damaged organs and the like. But what they were really doing was engaging in illegal cloning of human beings -- and even worse, they were trying to manipulate the clones so that they would be the ultimate soldier -- adaptable to any environment, super strong, super tough. Careful application of radiation was used on the experimental clones along with more direct DNA manipulation, try to create these super soldiers (it's not certain if the project was working with the US military or planned to sell these genetically modified soldiers to foreign powers), but all results to date has been failures, with the gene manipulation causing the clones to die quickly before they could be awakened. One clone only had been doing well with the treatment, but it was still kept in a state of unconsciousness as the scientists tried making him even more powerful with additional treatments.
One evening, as a storm was brewing outside, additional radiation treatments were being done when multiple bolts of lightning struck the facility. Ordinarily, a single lightning strike wouldn't affect anything, but the multiple bolts at once overloaded all safeguards (there were some witnesses to the strike that swore afterwards that the lightning seemed to bend towards the facility, as if some uncanny force was guiding it). As a result, the clone received a massive dose of radiation as well as electricity, and this caused the holding cell the clone was kept in to burst open, and the clone awoke. Up to this point, the clone had resembled an ordinary human, although one of apparent strength, but these twin energy sources caused an effect that made the clone grow larger, and scales began forming on its skin, with the hair falling out.
The NuClone (although he wasn't named this yet) was awake, but his mind was nowhere near human. There had been no education given him, and with the amazing strength it had, nothing could prevent it from escaping. He was motivated primarily by anger, feeling threatened, and he began a swath of destruction.
The newly formed Guardians of Justice (at that time, comprised of LaserAvenger, Avian and Dynamo -- and yes, I know I haven't written about the latter two yet... suffice it to say that Avian has wings and flies, while Dynamo has electrical-based powers) were called to deal with the NuClone, but they were soon able to discover that fighting the NuClone came with a price -- when exposed to a form of attack it hadn't experienced before, he adapts by increasing his strength and durability. This doesn't make him immune to that particular attack in most cases, but it makes him harder to take down. The trio worked on containing the creature as best as they could when a new superhero showed up on the scene, Nightstar, who hoped to join the team. Unaware of the NuClone's adaptive capabilities, she struck using several different forms of energy (as these are among her powers), causing the NuClone to become even stronger and tougher. She had been warned not to attack right away, but she had thought that her fellow heroes were trying to keep her safe, and realized she made a mistake quickly.
Eventually, the NuClone was subdued enough to be taken prisoner, and held in a facility especially designed for the incarceration of super-powered criminals... but he would return. The NuClone's first return resulted due to the actions of an attorney who took on the NuClone's defense on a pro bono basis, arguing that the NuClone couldn't be held without undergoing a proper trial, and that it wasn't mentally fit to stand trial. While the judge handling the case agreed with the Guardians that the NuClone was a danger to the general public, this attorney somehow got a release for the NuClone anyway, and when revived, it started a new rampage, which the Guardians fought to contain, although that rampage ended when the NuClone vanished before their eyes. It was hoped that somehow the NuClone's internal energies had caused him to be destroyed, but that was not the case.
Instead, the NuClone had been teleported to the stronghold of Death's Head, a villain who seeks nothing less than the death of all superheroes. Having had less than successful results using his Death-Droid mechanical soldiers, he had moved on to recruiting super-villains to work for him. Somehow, Death's Head was able to reach the primitive mind of the NuClone, and was able to keep him calm and contained until he was needed. After this point, whenever Death's Head's plans called for the need for mindless violence, the NuClone was brought in.
As a result of the mutation process, the NuClone's appearance has the tendency to change over time. These changes are usually a direct result of some form of attack made against him -- for example, the use of a sonic-based attack caused the ears to mutate so that these attacks were less effective. He continually grows stronger and tougher, while still apparently maintaining a very primitive mind. He appears to be unable to grasp language in any form, although can respond to a tone of voice (this may be something he'll adapt to as time goes on, as when the Guardians found themselves transplanted to an alternate reality where some of their friends were foes, while some foes were friends, the NuClone of that world had at least some intelligence and was able to speak, making him an even greater threat than the one on their world).
Trying to contain the NuClone if he can be subdued and captured is an ongoing issue. The first imprisonment involved the use of knockout gas to keep him sedated (there was no way to administer anything through injection, and nobody wanted to risk keeping him awake enough to put sedatives in his food), but this turned out to be a bad idea, as he was able to adapt to the point where a massive amount of gas would be required to knock him out -- a quantity that would endanger anyone downwind from the attack. He's too strong to simply be imprisoned, and research has been ongoing to find some way to keep the NuClone safely away from the public in a way that he can't escape from. Ideas have ranged from stranding him on a deserted island (discarded, as he could swim away unless an island could be found that would provide him with enough resources that escape would not be desirable, and even then it would have to be monitored carefully), launching him into space, or even somehow stranding him in an alternative dimension. It seems to be impossible to kill the NuClone, as his adaptive nature allows him to heal from wounds at an amazing rate, and even damaged organs adapt to be more durable when they heal.