“[I]s it ok to tell the "ugly truth" [about] how you[r] manager treated you during employment on the exit interview? I felt that [I] didn't [get] treated fairly during my employment. [So, during the exit interview, I gave a written description of everything that happened to me; HR made a copy of my statement and has asked my manager for an explanation, regarding what I described. I think that, perhaps it was not wise to write negative things, but I'm just being honest]. Just wanna know about your opinion guys! Thanks”
I understand the desire to explain yourself, and the situation that you faced, particularly if it was an unfair one. However, employers frequently use any negative information that you supply to them, against you. At this point, you're probably thinking, "What can they do to me if I don't even work there any more?" The answer is, "Perhaps nothing." However, if you ever have to list that company on your resume, and then, your new potential employers call the old firm on the phone, in order to verify employment... the Human Resources representative may indicate dissatisfaction with you by taking a very cold, or lukewarm tone, when confirming your dates of employment etc.
On the other hand, if you complain about your boss during your exit interview, your employer may start monitoring his/her performance more closely. If that boss was really bad, you might even get your job back (unlikely), or more likely... you might save some other employee the frustration of having to experience what you did.
Either way, what's done is done. Good luck!!!