In fact, it's basically empty talk. Give priority to praise, that is, the article is rigorous in structure, unique in conception, special in perspective and novel in thought. It's best not to have words like criticism, because it's all final. No more criticism will embarrass him. . But you should make some suggestions to show that you have really read this paper. This suggestion is an improvement on some shortcomings in his paper. You can write some suggestions that can be deeper and more detailed.