He will accumulate karma if he steals stat/ability/destinies from dead bodies regardless of whether they were killed by him or not. And something bad will happen if too much karma is accumulated. This only gives author excuse to hold MC from getting too strong and since the consequence is vague, MC will be made strong regardless whenever author needs him to. As a result, MC's varying strength and victories often feels like due to deus ex machina while missing a good chance to use regression as an excuse. The restrictions also feel illogical. In adventuring worlds, karma should not accumulate from looting owner-less things from dead bodies if they are not killed by MC. Otherwise Buddha would have accumulated tons of karma from eating already dead (cooked) meat regardless of how animal was killed with whichever intention. Plus there are good and bad karma but I digress.