unforgiving - Not making an allowance for error or weakness in others; not willing to forgive others for things they might have done wrong.
Because they knew that Alaska in the winter is an unforgiving environment, they had to plan their expedition very carefully.
negligible - So small or unimportant that it can be ignored or doesn't have a noticeable effect; insignificant in amount, size, or impact — too minor to be worth considering.
The difference in price was negligible, so she bought the higher-quality clothing.