What are some of the worst events a teacher can experience?

Not knowing every student's name by the second week of class. 

When a teacher try his best to deliver but gets not the desired result is the worst experience for him.

when students dont listen to teacher

Disobey and unrespect from the students during the class.

In my point of veiw he / she MUST know well the aim from the role of being a teacher and what is needed from him / her and what is the reuslt neede to be finished as well, meaning he / she MUST know the Goal of being a teacher.

When does the students not respect to thier teacher.

when he or she is obliged to do somthing wrong as giving a note to student who deserve more or less. or to be obliged to cheat in the work for exmple giving the corse of two houres in one houre

I would say if the teacher doesnt have the capability to deliver the concepts in an effective manner and doesnt have the strong understanding  of the subject well it will be the worst thing for him as he wont be doing any justice neither to himself nor to the students.

Giving a listening test to a class and finding out that the computer in the class does not play sound files--- nor does the one in the next class, or the next one.

After examining the plugs attached to computer #3, I found out that someone pulled them out just enough to render sound files inaudible. I plugged it back in and saved the test from total meltdown.

Unprofessional school administrations and unprofessional teaching staff could lead a good teacher to act in a disastrous way. Personally, I have mostly seen beasts working as school officials and teachers. It's a pitty for students who themselves need a lot of attention and discipline. Schools have become havens for chaos and recklessness. Many times I had regrettable outbursts and extreme confrontations with students; all because of the failing school systems. Everywhere I work, there is always a wrong person in the wrong place, and I always wonder why it is the same in all achools. But, the most shocking fact is that all schools have flourishing business, and they have excess of students. This makes me wonder what type of parents we have and makes me ask myself what type of society the Arab society is.

Mentoring students who have problems at home, distressing for both you and the student.