For me it has to be the lack of love and hypocracy! I think that when I went to bethel and could not believe what I saw there, it really pushed it home for me that there was something really wrong with the WT and jw's in general. Bethel was the most unloving, judgemental, and POLITICAL place I have ever seen! You always had to worry about what you did or said because the gossip was incredible! And even if you were really good...no actions to criticize, you always had your "trusty" housekeeper, that snooped through your belongings. She would have the audacity to say..."I noticed that you have condoms in your drawer...are you sure that you are protected enough??"!!!!!!!!!
When I used to complain to my jw mom about how bad it was, she told me that I was having a negative attitude and that was coloring how I saw things! So, I was the bad guy for calling it like it was! (All this, in addition to having an abusive elder husband!) I knew that I was done even back then....but it took me years of pain before I finally really left.