Best: many luckily. Constructive and thorough comments that help to improve the manuscript even if that means a lot of work.
Worst: fewer, still some. No or few comments are usually not that great; if accepted it is nice but still feels not fair and you are taken the chance to improve the work. But worse is when you get the comments that "all is bad", "key references are missing" (when you are at the reference limit), "the manuscript is obviously poorly written" (while 2 other reviewers mention it is well written) and other vague or even insulting comments that do not help to improve the manuscript at all. Personal attacks are the worst and should be forbidden ;)