So some npc are both hostile and immortal. You beat them till they are kneeling and then they get full hp again and start bashing more at you.. rediculous

yes, they are most likely:

a: quest related
b: children


Damn children...

You can't play your game that way. Killing certain people? Bethesda absolutely will not allow that!

If you're on the PC, you can use the console to remove their essential status. I forget how (I think it's setessential 0, but I'm not sure).

I posted about a Guard who accosted me in the middle of nowhere and insisted I pay 1000 gold. No matter what my Follower and I did, he wouldn`t die. In the end I gave in and paid the 1000.

He was just a generic guard. It made no sense.