As to what was going on in Fury.. I had some ideas last time I watched that ep (which was fairly recently). Firstly it highlights how we know NOTHING about Ocampans and how Kes herself knows very little about them. They are a stunted people as they exist on their own planet. They have enormous potential but when Kes begins to manifest that potential she has no role models, no idea what will come next. No training, no guidance, no clue.. imagine a Vulcan going through Pon Farr in a cave by himself without ever having heard about what it was or seen it. He would go insane! And might well try and kill the first people who approached him because he had no context for what he was experiencing so was highly threatened.
So Kes experiences changes for which she has no preparation and which terrify her--her lashing out and blaming it all on her family is typical of what adolescents go through--X 1000. For all we know it WAS a kind of adolescence, a maturing from youth into something greater. Obviously there is more to the Ocampans than the nine simple years Kes originally thought her lifespan would cover.
So Kes's response to her changes is much worse because she has no cultural context for it and it is terrifying. Her lashing out would not be as much of a problem if she was lashing out at other beings such as herself.. but she has no peers and the only ones she can blame are the only ones she has been in any kind of relationship with. Unfortunately they are in no position to rein in her anger because they are so weak.
I can see your point when it comes to the adolescence thing but the events in "Fury" still doesn't make any sense.
OK, a situation could occur where Kes could be p***ed off with Janeway and the others. But she would never try to kill them or harm them in any way. Such behavior would clearly be caused by a mental disorder and I don't like to see Kes portrayed this way. No other main character of Star trek have ever been thurned into mentally sick people and remained that way.
Some would say Dukat was turned into a mentally sick person and remained that way, just as an aside here. But I'm not saying she was mentally ill.
How do you know she would never try to kill them while in some adolescent rage? How many teenagers have yelled "I HATE YOU YOU'RE RUINING MY LIFE!!!" at their parents? That's basically what Kes does but magnified times a million. Now imagine such a level of anger and blame directed at Ocampans who were the matured version of whatever Kes is about to become -- beings who cannot be killed, maimed, destroyed by that anger, beings for whom this is the equivalent of cursing your parents out and slamming your bedroom door. Picture her behavior directed at Q for instance, it's a great big tantrum.
Besides that, Kes wasn't the typical neglected teenage kid. First of all, she had nothing to blame her crewmates for. They, especially Janeway, treated her in the best possible way. Second, Kes was a smart, level-headed strong-willed person who did show several times that she could overcome evil temptation and attempts from evil forces to control her. She was probably the last one on that ship who would have gone crazy in any way.
Well plenty of lovely smart 12 year olds who enjoy going shopping with their mothers turn into horrible emos who blame their parents for their existential angst and have hair trigger tempers. It happens and there's even a physiological explanation for it in humans to do with the development of the adolescent brain. Also nice as Janeway and the crew were to Kes they were unable to give her the guidance an evolved Ocampan would have given her because they simply had no idea.