The antonyms for the word "more excusing" could be "less forgiving", "harsh", or "implacable". If someone is less forgiving, they are not as likely to give excuses or let things slide. Additionally, if someone is harsh, they are not as lenient or flexible with their understanding of someone's actions or behavior. Finally, if someone is implacable, they are completely unforgiving and unwilling to make excuses for others. All of these antonyms suggest a lack of patience or understanding, which is in direct contrast to the more excusing behavior of being forgiving or understanding.