I voted to close this question, because you are asking us to tell a story that takes place in your world, not to help you with building your world.

No, I am asking for stats to build that story around. Asking how a fight would likely go down in a real world or a place that is realistic is not trying to get folks to tell a story for you, but rather how you need to build it to be a solid and believable tale. I can say, for example, that Hulk only killed 10 or so people in its rampage and be done with it, but readers and probably the writer will feel like that is bullspit and and readers/the writer's own mind will tell tell the writer to do more research and math, as it should be around 500-1000 kills. This is why I am asking.@Philipp

In order to do that math you have to tell a story. "Hulk killed only 10 people" is perfectly plausible if you tell a story where he only gets to kill 10 people before getting apprehended. And so is a story where he kills 10,000 people before he gets caught. Or one where he kills nobody at all, because you are writing a saturday morning cartoon for kids where he is only allowed to do property damage. It's up to you as the author to write the story how such a rampage would play out and how many people would die during the events of your story.

Maybe something like this might help narrow it down: In a fight between a thing that has the intelligence and size of a human but otherwise the physiology of a cockroach and a farmer with a shotgun/local police/National Guard, who would win? Although it would still be asking for a plausible outcome of something that is completely impossible in the first place.

I understand what you are saying, but regardless, it would be helpful to have a bit of a guide in terms of kill count and whatnot to work around. This question is assuming this is a 'realistic'(as mush as it can be while still happening) scenario. That is the point of this SE, to help builders make their world better. If I get the data from this question, that I will keep it in min while writing the story, as to add an extra layer of believability.to it. @Philipp

The bodycount part of this question seems to assume that the whole scenario can be reduced down to some kind of math equation. Like, if the monster moves at X speed and people are spaced Y distance apart then calculate Z people it can kill per minute. Has anyone ever heard of a precedent of calculating such a thing and for that calculation to have any relevance to reality? For instance, if a tiger escapes a zoo, is it at all useful to try to calculate how many people per minute it will maul? How would any such calculation be relevant to the particular circumstances in reality?

So if a killer gorilla go out of a zoo, you would not like even a rough estimate of the deaths, injuries, and damages that could occur? Anyway, it is relevant because it helps me decide some of the details of my story, lest a reader or my future self screams at my 'stupidity' of having a giant roach at least exterminate a neighborhood and only having like a handful off kills before it is slain by gunfire that may or may not be realistically able to fell it. @TheUndeadFish

Well, at least it doesn't include [science-based].... You've violated conservation of matter and energy already - why bother about the rest? The realistic part ended when it gained body mass out of nowhere.

@ConanHighwoods "So if a killer gorilla go out of a zoo, you would not like even a rough estimate of the deaths, injuries, and damages that could occur?" liking some information and being able to reliably provided are two completely separate things. How many dead and injured can a hoplite leave? What about a WW2 soldier? What about a roomba with a knife duct taped to it? Or a guy with three arms and a trombone? Or a tank? Most of these are well-known, unlike a mutant cockroach. And we still can't provide a reliable number of casualties because that's not how we produce estimations.

With all that said, the whole estimation thing is a complete red herring because it's not a worldbuilding problem. It's, at best, a writing prompt to throw at somebody.

You heard 'em chief, all fantasy WBs nee not ask!!! @Therac

Ok, so I guess it is a bit more plot based, but I still think it relates to my world building. Also, not really a writing prompt, more of a 'what-if?'. @VLAZ

"Also, not really a writing prompt, more of a 'what-if?'" I fail to see the relevant difference here. It's still something not related to building a world. At best, it is aimed at building a story.

@ConanHighwoods Worldbuilding means building world rules. Your premise defies the basic laws of thermodynamics, which are the rules of our world. All answers to it are equally valid. Maybe 1 person, maybe 8 billion.

Not really. Sure the backstory and some of its biology is fantastical, but that does not make it fully above realism. I am falling to see why you guys are so caught up on the square-cube law when people are asking questions on their worlds that have flippin' magic in them unlike mine which is just a fantastical origin story for a mutant cockroach. Like do you guys hate worlds that even deviate a micrometer from ours? @Therac

Eh... a cockroach gaining mass out of nowhere is 12 oz. Mouse kind of mechanic. It's not even Beavis and Butthead. Per 12 oz. Mouse rules, I guess the number is 8 billion.

Can you look again at 'a cockroach… was microwaved… resulting in a roughly man-sized killer cockroach'? How can you justify that? How did any 'roughly man-sized' creature survive being confined in a microwave?

@ConanHighwoods Then why not write it according to those rules - Terra Formars anime and manga where they send cockroach and moss to Mars and the radiation mutates/evolves them in to humanoid, 8 foot tall killers, in 500 years?

I could, but I was trying to see 'realistically' how deadly 1 would be IRL if this somehow took place. @RobbieGoodwin

Does 'IRL' mean 'in real life' or what, please? Why is it not clear that how deadly one would be is 'almost not at all'? Was what you meant to ask, how deadly could the offspring from one become, which might matter much?

Yes, "IRL" means 'in real life'. How would 1 not be deadly? I just wanted to see how deadly a single instance of this creature would be, for the story and for that fact I might make this a swarm rather than just 1. @RobbieGoodwin

Sorry - are you Asking how deadly the bite of a single critter might be, in a one-to-one confrontation with a man, horse, skunk or whatever, or how many victims that single critter might bite? (I'm guessing roaches inflict trouble by biting, and I stand to be corrected on that, at least.)

In this case they can wield weapons and/or punch, but a roach's bite at that scale can probably remove some digits and maul your face beyond recognition. In this case mutoroach vs humans. @RobbieGoodwin

@ConanHighwoods Why did it take you two days to mention that they can wield weapons and/or punch, but a roach's bite at that scale can probably remove some digits and maul your face beyond recognition? Do, please, go to Chat!

Ok, will do. @RobbieGoodwin

Let us continue this discussion in chat.