this is, unlike Nemesis, a pretty accepted character idea. at least, given the lore involved and the plausibility of it, I personally don't see why not. but then again, I'm biased to a degree. "My name is Bolter. I am a Spartan designated with destroying an Inserectionist Base on my own. would you like to continue pestering me?" Bolter, having been "Pestered" by a minor character of a Medic who was trying to get them to the Infirmary for a broken nose they sustained in a fight. Bolter is a Spartan II with no special deviancy from the standard Spartan II's, and while she is considered MIA, she is very much alive, and kicking any Covenant who dare get close right where the sun don't shine. which happens to be down the throat for any Covvies that get in her way.
Born to two farmers on a rural farming world that was originally a UNSC planet, but since was fought over by the Insurrectionists' and to this day, minus the Covenant war, they'd still be at it. while she was a dedicated and loyal daughter to them, she also had all the genetic markers of the Spartan Program, and was extremely quick-witted for her age, often allowing her to outthink her enemies. another trait she showed was outstanding level-headedness, especially when her friends were in danger. however, her troubles didn't really start until mental tween years.
Ages 6-10: during this time, the basic training endured by all the children of the Spartan II program was endured by her. however, she displayed remarkable obedience to John, and while they never met in person, they were often in the same fights until Augmentation took place, as she would invariably find herself in the same squad as John or Kelly. there was only minor disobedience from her in her early years, mostly because of her lip towards senior officers. she would openly disrespect them, and while she'd never go out of her way to attack them, she came close when it came to several of the Trainers, who appeared to be extremely ruthless in forcing her to the proverbial wall. Ages 11-20: this was by far the most interesting time of her Spartan career. while she was exceptional in the various trainings she'd do, she also found herself in different situations that she was trained for on a regular basis. this led her to become highly adaptable, and while nothing about her is "easy" before her Augmentation she was considerably less... surly. Augmentation: during and directly after the effects of Augmentation, she was gifted with the standard effects of her Super Soldier bretheren. super speed, reflexes, agility, endurance, strength, and her mental ability, which was already higher than her average Spartans, was even higher than before. however, the loss of those she had trained with left a deep scar on her mental ability, making her withdraw into a state of depression for short period, before eventually coming out even more surly than before, and highly aggressive. she no longer took the easy way out of arguements, she would fight tooth and nail for what she believed in. this led to her almost being expelled from the Project, but quick word from Halsey and she remained in, despite wounding a CO. Battle Record: in order of chronological time, she has completed many field missions deemed not-quite essential towards her story. during her time before Mark IV power armor, she fought many insurrectionists, destroying and compromising at least a half dozen bases with very little help or cover. she also, during the Human-Covenant War, was the first of the Spartans to secure a kill on a Hunter, besides the obvious time where John, Sam, Kelly, Linda, and the rest of the squad destroyed a Covvie ship. she did so by delivering a killing blow with a Rocket Launcher to the back, having dumped two rounds into it's shield previously. as well, she has been reported and confirmed to have taken down a half dozen Zealots in single, melee combat, usually with just a knife. she has destroyed two battle Carriers that, while they were minorly guarded because of the massive amounts of troops on the ground, they were dispatched by taking out the Fusion Reactor both times (Confusion as to what a Covenant Ship uses as a engine, someone, if you could help me, that'd be great). one instance was in a Covvie attack on a moderate Military planet where a new MJOLNIR armor was being developed for a time (I don't care to list which, so if you're curious, I'll just tie it into a variant armor or something) as this is, this is a WIP, so please bear with me.