How many people could an immortal warrior kill in a thousand years?

[Lvl 2 Expert]

She's going to need quite a big helping of immortality/healing factor to realistically pull this off, that much I can say. Sure, after the first few hundred killings she's more experienced at this than anyone ever, but with the amount of kills she's doing she's bound to run into bad luck somewhere. Just the odds of a normal person in an office job getting mangled in a traffic accident get pretty high over a 1000 year lifetime.

For the number of kills I'm going to assume she has some sort of a moral code that means she's not indiscriminately killing. If she just goes full murder hobo every week the numbers get pretty big after all. If she just starts slashing people up until either she reaches her number or she's reduced to enough of a pulp that she might as well be dead (and I'm pretty sure someone would try to drown or burn her or something if she started to regenerate from that anyway) the story would be a lot shorter than 1000 years, or at the very least contain a 990 year break where she's trapped in a coffin on the ocean floor or something. And if she starts working in healthcare and murders old people on the brink of not making it anyway I am going to stop reading. So, she does semi-morally defensible killing. She is a mercenary, privateer, pirate killer, executioner, bounty hunter, even a freedom fighter at times. It doesn't need to be legal, but there needs to be at least some group of people who want the killing to happen and who are happy with her contribution. How many people can you kill living like that? Well, it's going to depend a lot on when and where. There will be periods with wars going on. With a good enough immortality powers you can get dozens of kills in a single battle if it gets bloody enough. (If she has to worry about getting wounded than this is the first one to be out.) But full out open battles are rare. You get maybe one of them in a year of service, together with some smaller skirmishes and fights around besieged cities. Combined with a little random vigilante work, kill of a few pillaging and worse colleagues every now and then when nobody's watching, and you can get to 50 per year with a good war going on. Of course there's usually a war on somewhere around the world, but between the trouble in getting there, complications like the amount of languages she speaks etc I'm estimating she will still have a lot of downtime. The rate goes up and down quite a bit throughout history, but let's say there are 4 peace years for every war year, and of those war years another quarter are the good ones, with the others good for maybe 20 kills.

Now the years in between wars won't all be dull either. If she can survive getting shipwrecked she could do some privateering or pirate hunting and get some of the most productive years of her life out of that. A hundred kills a year isn't weird if you're pretty much allowed to off an entire ship at a time. Sure, she will have bloodthirsty colleagues as well, but not bloodthirsty enough to start arguing with the mad person stabbing every downed enemy as if they were going for a high score. So let's say for every good war year she has she has another good naval year. But these opportunities come and go. So there will still be plenty of boring years left where she offs a highway bandit or an abusive parent here and there, works as an executioner a bit, some bounty hunting or assassination if the possibility comes up, let's say 10 kills per year. So in a thousand years there are ~63 good war years, ~63 good naval years, ~188 average war years and ~686 regular peace years, for a total of ~63*50+63*100+188*20+686*10~3150+6300+3760+6860~20 .070 kills. So around 20k is my best guess, or around double what you could get with "dull" years only, coming out to a bit less than two kills per month over the entire run.

If she has to worry about getting hurt even a reasonable bit and has to kill sneakily you can basically scrap all the good years, and she'll have to work pretty hard to get to 10k, and stay off of the death traps they call ships.

[Max_Killjoy]

I'm writing a fantasy story about a peasant who prayed to the goddess of war to save her home from an impending invasion; in exchange, the goddess demanded a certain number of souls to be delivered to her, and cursed the girl so that she couldn't die until she had done so.

The story I'm telling takes place a thousand years later when the woman is near to finishing her task, having been killing people professionally (sometimes as a barbarian, sometimes as an assassin, sometimes as a mercenary, sometimes as a pirate, etc) for the last millennium. This is all in a pre-modern setting; I'm thinking she made the bargain in the equivalent to the bronze age, and the present day is late medieval. And only personal kills would count, not for example ordering someone else to do the deed. So I need to work backwards from the assumption that she's almost finished with her task after a thousand years, and figure out how many souls she was tasked to deliver to the goddess of war in the first place. If the number turns out way bigger than I think the number of people she saved is, I can always say she owed some significant multiple of that number (like "seven souls for each one saved" or such). How do I go about estimating this?

Are there restrictions on which kills count beyond "personal"? Does it have to be someone who deserves it, or who is willing and able to fight back, or something else?

Can she tell if a kill would "count" beforehand?

Might make for some interesting "detective" stories, where she can tell that a kill of say an accused murderer wouldn't count, but to keep someone else from executing him instead she'd need to figure out who actually committed the murder, and then kill them instead.