I love this question.
Assuming they get to keep their real world ID and certifications but do not have family or friend connections.
Circe- Might snap and try to kill me at first, but eould be so happy to be removed from her situation she would go start a bookstore. Would probably force me to give her money.
Fedor- Would return to Russia and start a butcher shop. Would try to stay out of the war. He would not hold a grudge nor would the situation bother him too much. He'd start working out, try to slim down, and find a good woman.
Ebony- Would start a general practice in the states. No hard feelings. Would have trauma knowing her family doesn't exist in this world. But might start a new family. She might try to contact me with questions.
Mark- Would try to kill me if he couldn't return to police work. Is the kind to hold a grudge. If he could return to police work, I better never enter his jurisdiction.
Carson- Would get a part time job and try to survive. I would not want to bump into him.
Banko- Would return to office life and not care. Would consider having no family and the wiping of the slate of former contacts a boon.
Nickey- She would have assassin skills. And a grudge against being a character. She's also immature. I would be hunted down and killed off in a way that would never implicate her.
Kunchen- A pacifist. He would return to the moutians and meditate. This would all be part of the universal flow that he has little control over.
Zak- Would seek me out and slit my throat, then go back to Africa to set-up illegal poaching operations.
Mike- Would find himself a mental institution after having a complete meltdown but would be too insane to cause me any harm.
Shelly- Would remain Zak's love interest and follow him about.
Mandawuy- Returns to Australia and starts a business after these realizations hit. He'd fail to disuade Zak from murdering me and doing crime and might find himself back in the poaching operation if he is not careful.
Eduardo- Would become an alcholic and drink himself to death. With no friends in this world, his fate would be inevitable.
Valentin- Would not be bothered about the situation and treat this third reincarnation as a new start. Most likely would become a professional runner.
Lin- Might very well hold grudge. Would write songs about me with unflattering lyrics in her attempts to become a pop idol in this word.
Phaolo- Would stay by Lin's side and support her. That would be the most important thing for him.
Chien- After learning he was just a character from an obscure barely read webnovel he would hit the bottle hard. A high chance he'd snap out of it and use his credentials to return to the police force.
Sundara- Would be devestated that his family did not exist here. Would be relieved to not be a mascot character. He would return to school and work on becoming wealthy and powerful. Knowing that his author doesn't have power in this world, he would plan to contact me with many questions. But he would ultimately decide to let his grudges go.
Janel- One hundred percent hunt down the bastard and kill. She would be smart about too, making sure to build upon her life in this world to be powerful enough to make something happen through proxies.
Lizbet- Would return to compulsive gambling, but with no money she'd have to go to work. The weight of knowing would be hard on her. Eventually she'd end up insane, homeless, or in a bad relationship. Would kill me impulisively, but only if we met.
Darrone- Would seek out Megan first. Most likely would remain nuetral and try to get by using his blue collar skills and math ability to work for mining companies despite having died in a mining accident. He would not kill me, but would want answers.
Megan- Would go into a shelter and not come out unless someone cared enough to find her. The knowledge would break her at first but eventually she'd become numb and just try to survive.
Alfredo- He would be pissed. But since he had no family would find himself in the same situation but without his extensive connections. He'd become so involved rebuilding his life, working physical jobs that are a bit too demanding for him, and getting his shit together that he wouldn't have time for vengeance. If he found Circe, and also knew she was a character, he'd try to help her out and make sure she wasn't homeless.