[xxs]

You should be transparent about what you do not appreciate (e.g. randomly copying code from unknown sources). About back and forth PR comments, just sit next to them (or call, if remote). I rarely leave a lot comments on pull requests, if the issues is not simple.

Also you should be upfront with the management about the quality of the developers.

In the end I suppose it's more about being afraid yourself of confrontation. There is absolutely no reasons to dread your work (pull request or anything else)