Mine was more the thousand little cuts that bled me to death, with a few big AHAs that bled the JW completely out of me. A couple stick in my mind, like the time in 2012 I visited the local cemetery and looked at the old graves (100-130 years old; my area is not very old in the scheme of civilisation) and I noticed that many of the old graves were those of children, teenagers and young adults. Comparing to the new graves who were mostly of people in their 70s-90s, I thought, "How could the world be worse to live in than ever before when people are living longer than ever before? How can it really be the last days?"
Another time, by the time I was having doubts, in late 2012, I bought a King James Bible and started reading it to get another perspective, and suddenly it hit me that Jesus' actual message was far different and far simpler to what the WT says it was. I had an incredible moment of revelation.
The next big one was when the Inquisition arrived at my house and grilled me for ages about so-called 'apostate' stuff I put on Facebook. Oh boy the thought police hammering me made me realise they had something to hide.