I mainly get really nice comments from my readers but, I do come across rude ones once in a while. Hmm, let's see... The worst would be:
"If you are truly busy with your personal life, I suggest you abandon the story and focus more on shorter stories instead"
And also, not bad comments but, I get this SO often:
"Why is it so short? At least update longer"
"Too short. Please update more"
"That's all? Are you kidding me?"
"What's the point in this story if you update so short?"
And this is DESPITE me clearly telling the readers at the end note of the first chapter that I can't update longer or more often because I have a full time job. Again, not a negative comment but, it's rather frustrating to know some of my readers do not even bother to read my author's note. Like, what else am I supposed to do to explain my situation? Give out personal apologies? Sigh... 
I don't want to end up to a point where I dread reading comments in case I see more complaints but, you win some, you lose some, I guess?
I'm certain I will get worst comments in the future so, I'm trying to practice having a thick skin to deal with it.