The worst response?

 When you teach a class, the best student response is an actively engaged participant who obviously enjoys the lesson or activity.  Of course, you may also see students going through the motions who obviously do not like the lesson or activity.

If you ask both groups for feedback, you will likely get very good reviews and some not so good reviews. You may also think that the less than enthusiastic feedback is the worst response.

It is not.

The worst response is the non-response; the students who ignored your request.

Positive feedback helps you judge whether or not to repeat that type of lesson.  Negative feedback helps you make adjustments so that lesson is more engaging next time.

No feedback suggests no engagement at all.

Don't design lessons that only get good reviews.  Design lessons that inspire a reaction from all students.