Hmm, I think some of these criticisms are more on target than the ones in the OP, but I think some miss. I'm not going to go back and look at every fight, but my recollection is:
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The first few he's in kind of a "WTF?" space - he's been put into this dungeon and doesn't get what the hell is going on, but he has to kill stuff to survive. As he figures out more of what's happening, he has more empathy with the mobs/bosses.
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The ones he feels badly/guilty/pity for are the ones who appear to be real people or aliens who have been made to play the part of mobs, bosses, or NPCs. Some of the others are described as total constructs, or as beasts from some alien planet, and he feels less badly about those.
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I'm not understanding why in one paragraph you say that Carl never shows any regret or anything about the hoarder, and in another you ask why she's the only one we're meant to feel sympathy for? My take is that he does express regret and sympathy for her, and he does so for a number of the other subsequent mobs after he figures out that they're actual people/beings.
These aren't great art, and I don't think I've seen even the big fans say that they are. They're fairly simplistic and somewhat heavy handed, but I think some folks here are conflating the racism and sexism that's criticized in the book with support of it.