Robert Hunter was born in Scranton, Pennsylvania. Due to genetic alteration carried out on him by the Kree; Lunatic Legion, Robert gained the ability to explode and reform himself at will.
The Lunatic Legion send their agent, Nitro, to steal a top secret government nerve gas called Compound 13. He is confronted by Captain Marvel who defeated Nitro by having Rick Jones hit his Nega Bands together at the moment Nitro explodes. The gas canister was ruptured in the explosion and Mar-Vell successfully resealed the container. However the exposure to the nerve gas will ultimately lead to Mar-Vell's cancer.
Omega the Unknown
Nitro reappeared and is looking for revenge against Captain Marvel, briefly mistaking Omega the Unknown as him. Angered by the villain's attack, Omega chased him to a warehouse filled with Stark Industries technology where Nitro hoped to draw out Iron Man, and Captain Marvel. Omega engaged him in battle, ending it by clamping a titanium tube over Nitro just before he explodes, causing him to shoot his atoms up into the sky, but also causing the ceiling to collapse on Omega.
Return of Captain Marvel
Captain Marvel returned from space and resolved to find some kind of life for himself now that he is separated from Rick Jones only to end up battling a revenge seeking Nitro.
Nitro joined Thanos'Defenders an organized group of super-villains that was in the quest of finding and obtaining the Oracle of Ancient Knowledge. They apparently disbanded after the mission was successful.
Nitro battled Legacy (Genis-Vell) who wants to kill him for his part in his father's death, however, he decides to just arrest him after reading a quote by his father on a display in a museum on Hala: "Defeat your enemy, do not become your enemy."
Heroes for Hire
The Heroes for Hire batted Nitro in the Alantic Coast Rail Yards. Hercules defeated Nitro by throwing a tanker of natural gas, forcing him to disperse, risking his teammates' lives. Iron Fist realized that Hercules is drunk, much as he was when he attacked the U-Foes.The Heroes confront Nitro and Dane Whitman decided to become involved as well. Black Knight rode his magical steed, Strider, into battle against Nitro. Iron Fist stood up to Nitro, but even his iron fist is no match for his enemy, though the resulting explosion sends everyone flying. Nitro was about to kill Iron Fist when Black Knight stepped in to protect him. Nitro attacked the Knight but using his Shield of Night, Dane absorbed the energy of the blow, re-directing it through the Sword of Light to explode the ground beneath Nitro, knocking him out with shrapnel. 
When Nitro was hired to kill Tony Stark a fight developed between him and Iron Man. Iron Man, whose sensors and telecommunications gear had been recently upgraded, noticed that every time he exploded, a high-frequency pulse was emitted by his body. Experimenting, Iron Man duplicated the pulse, causing Nitro to explode. After he exploded several times in a minute, he passed out from exhaustion (presumably, it takes energy to explode, and he could only spare so much before he passed out). Iron Man handed him over to S.H.I.E.L.D., along with a recommendation on constructing a null-harness. He was sent to prison.
Nitro battled Iron Man along with Count Nefaria's Death Squad and Whiplash. Nitro now wore a defensive scrambler to keep Iron Man from remotely activating his powers as before, but Iron Man shot it and set Nitro off, using him against his own side, who swiftly retreat.
This explosion apparently killed Namorita, Night Thrasher, Microbe, and the supervillains he was with during the raid, along with sixty children at the nearby elementary school and the surrounding neighborhood in the town where the fight took place.
Knowing that Nitro's explosive power could not be that great (at least not under normal circumstances), Wolverine began hunting him after he escaped in the back of a pickup truck. Nitro was found by Wolverine and a group of S.H.I.E.L.D. agents, but used his powers to kill the S.H.I.E.L.D. agents, and seemingly kill Wolverine. Nitro then took a phone call to an unknown government official who may be involved in the aforementioned Stamford Incident.
After the phone call, however, Nitro found himself in the grip of a nearly fully regenerated, and enraged, Wolverine. As Wolverine pounded on him, theorizing correctly that Nitro's powers couldn't affect anyone or anything in very close proximity, Nitro revealed that he had been taking Mutant Growth Hormone to increase his powers, hence why he was able to cause the disaster in Stamford. Nitro also hinted that there was someone bigger behind the events of Stamford, but before the name was given, the two were confronted by the three mystery agents. They were revealed to be Atlantean Royal Guard sent by Namor to apprehend Nitro for the murder of Princess Namorita.
During his battle with Namor, Wolverine was knocked unconscious and the Atlanteans took Nitro to New Pangea for torture and interrogation. Wolverine pursued them in the Iron Man Armor and "negotiated" with Namor to see Nitro, only to find that Nitro had killed his interrogators. Wolverine cut off Nitro's arm at the elbow. As Nitro begged for mercy, Wolverine recanted on his promised protection. He allowed Namor to do what he wanted with Nitro, who stayed as a "guest" of Atlantis. His secret benefactor was revealed to be Walter Declun, the CEO of Damage Control.
Cell-13 an Atlantean splinter cell lead by Kamar; Namor's son, who had been siphoning Nitro's power to create a weapons to attack the surface world. Namor decided the city had been compromised and he had enough of the involvement with the humans, he decided to evacuate the city through old tunnels running through the ground, the civilians would live amongst the humans, not in one city any more. He made the preparations for the destruction of Atlantis, he would use Nitro whom was still in his jail to blow up the entire city like a time bomb and chain his son to the crown to die with the Nitro and the city as punishment for his betrayal. The city was evacuated and then blown up and completely destroyed only leaving some wreckage behind. But Namor and his army found refuge in Latveria.
Nitro escaped Atlantis to the sewers with a few Atlantean terrorists. He was later captured in Latveria and held in Castle Doom's dungeons by Doctor Doom. Penance later attacked Latveria and forced Doctor Doom to release Nitro, who Penance tortured and almost killed, even forcing Nitro to wear the painful costume. He was found by the Thunderbolts, many of whom were shocked at the level of the injuries. It can be assumed that Nitro was arrested by the Thunderbolts.
The Hood's Gang
Nitro joined up with the Hood's Gang. They stole a treasure from an Arabic diplomat, then had a celebratory party were the Hood shows them how he's the leader and the ways he delegates the job.
Self-Explosion: Nitro possesses the superhuman ability to literally turn himself into a living bomb. Nitro can blow up his entire body at will and exists in a sentient, gaseous form until he reconstitutes himself. Typically, Nitro's maximum blast force is equal to about 250lbs of TNT. However, while taking Mutant Growth Hormone, his power was enhanced far beyond his original limits, sufficient to level the city of Stamford, Connecticut.
After he explodes, he can reconstitute himself at will and can remain in this gaseous form for an indefinite period of time. Nitro also generates a type of kinetic field around his body that also allows himself to reconstitute the clothes he wears at the time he explodes.
A high-frequency pulse is emitted by his body each time he explodes. Iron Man duplicated the pulse, causing Nitro to explode. After he exploded several times in a minute, he passed out from exhaustion.
If separated or dispersed, it will be longer or impossible to reform. He cannot reform if partially trapped within a forcefield.
During an encounter with Wolverine, it was discovered that if an individual can get close enough to Nitro, less than a few feet, it nullifies Nitro's ability to explode and leaves him as vulnerable as any ordinary human to physical assault.
He is also missing half of his right arm, which was hacked off by Wolverine.