If you know that your colleague is sensitive to what appears to be the overwhelmingly “negative” comments, make sure that there are positive statements. I had a code review recently for one of my guys that had a lot of comments that were style and logic problems.

When I finished the comments on the code, I made sure I added a comment to the top of the pull request (we use BitBucket) indicating that it was clear he understood the point of the code and had written a good first pass at it, but there were a few things that needed to be dealt with for idiomatic code.