HEADCANON - Jamison and life growing up in the Wasteland
While it's not specified, the Omnium explosion occurred probably when Jamison was around 6 or 7. So whilst he has some vague memories of his life before it, most of his life has been spent in this post-apocalyptic style of life.
For the first couple of years post-explosion, Jamison lived with his parents and a small community of people that lived primarily in their town - with a base at the town library basement once people began to leave their houses and live more so together. Here he, like other children, were kept mostly indoors as the adults went out for supplies. Here, he played with other kids and read a vast majority of the books in the library - also being taught various subjects as well. He took particular interest in learning chemistry, and all about demolition and explosives from his dad - who was a demolition specialist. Then the town was attacked by other survivors more desperate for space and supplies. Everyone scattered, and Jamison left town with his parents - leading to a more rural life. His parents, especially his mechanic mother, got supplies through fixing up vehicles and constructing makeshift weaponry. It was then that he began to develop those skills that became his forte later in life, and it was unfortunately here that he became more and more exposed to radiation (more to come on that another time). Supplies were pretty scarce, and the family grew more used to going to bed hungry. This lifestyle took them more on the road, travelling between places and leaving before things got too hostile. However, one day, a skirmish broke out between human and omnic survivors nearby - all fighting over increasingly limited resources. His parents tried to hide and wait out the fight, but were killed when burglars broke in - the young Jamison spared but left with no-one. Some of those left, a group of local bandits, took pity on him and took him on the road - using him a as a scavenger to collect and steal supplies from the Wasteland. From this, Jamison got his alias 'Jun.krat' and where he learnt how to build weaponry of his own and protect himself in this 'every man for himself' way of life. His caretakers gave him food and basic shelter, but everything else he wanted or needed, he needed to get himself.
Eventually, his confidence in his own skills grew and he went off on his own - stealing from the caretakers and moving on his own. At first, he built up a reputation as an arms manufacturer and dealer - building and trading his own weapons for increasingly good supplies. Yet eventually he decided to use them - taking inspiration from the supervillains he read about. He turned trade meets into ambushes, robbing buyers blind without giving a thing in return. That then lead into him becoming a highwayman for a little while, particularly focusing on gaining weaponry and explosives.
At some point, he made his way to Jun.kertown and bought his own little workshop. Now with a safe base to store everything, his inventory and his plans both grew. He focussed in his work on explosives and began to specialise in robbing buildings using said explosives. He grew an increasing amount of money on his own, which he buried in a secret location. It's also in Junk.ertown that his experiments surrounding land mines and his RIP-tire once failed, leading into the loss of both his arm and leg (thus blossoming many jokes). Within Junk.ertown, despite the presence of community, Junkrat still acted on his own - outside of helping arena fighters develop some of their weaponry. He stole, he experimented, he acted with little more than shallow consideration for his neighbours. He wasn't very popular.
Though in a community of people refuge from a very independent, survivalist, traumatised society, cooperation was often based out of fear and violent prowess more than anything else.
So in verses where Jun.krat aligns either with Talon or with Overw.atch, it's at first very hard for him to assimilate. He doesn't remember well what actual society is like, has never experienced a team or real friendship - outside of Roa.dhog of course. Betrayal and death were always around the corner - forming deeper connections often was a detriment and most people didn't. So he isn't well versed at all in social norms, expectations and faux pas. Eventually, he begins to try and make friends, but both his unstable persona and his lack of friends throughout his life make it so he really doesn't know how to do it. But he tries, often just following his thoughts wherever they go - at least being entertaining in the process.
Other little aspects: he hoards food and supplies due to being used to scarcity; he is quick to enact violent revenge on those who cross him because that's how it worked where he grew up; because it's what his idol villains would have done and because that's how he expresses it; he isn't used to cleanliness because water was a rare resource and it was wasting it if you didn't use it either to drink or as a coolant - resulting in permadirt on his body, which didn't help his skin since it was irradiated.
