Nah, for me it was the evidence of my eyes. In the Bible when the Spirit came upon Jesus' followers they were able to Speak in Tongues, which allowed them to say something and EVERYONE understood in their own language, but nowadays speaking in tongues is babble-speak only understood by somebody else touched by God who seems to continue to speak as if he was from the 16th century. I remember being frustrated by a being who supposedly knew everything speaking, "Yea I say unto you that if you speak with Me I will tell thee..." So forth. I also was always amazed that either the person speaking in tongues spoke for 10 minutes for a 30 second translation, or the translation was like 20 minutes of ancient English for 42 seconds of tongues-speak where they said "Ashumdelalah" 16 times.
Then the "three in one" frustration was a big player in my huge doubt that began nearly when I first heard it. This played into the Sacrifice story that was also frustrating to me. God, who knows everything and is everywhere sends himself to "die" on the cross knowing that he would rise again in "3 days" that were counted as a full day if any part of it happened in any day... Also this God would know that an eternal spirit can't be killed. Then this God holds a conversation with himself and forsakes himself? I was nonplussed. It just doesn't seem like a sacrifice or even a game if you already know you are going to win. It's like playing chess with a 3 year old who doesn't yet know how the pieces move, how is that a challenge?
I was told that if you even had the "faith" of a mustard seed you could do anything Christ did, like walk on water, heal the sick, etc. Shoot Christ said you could move mountains, I have seen none moved. I've met nobody, and I really do mean nobody at all, that could do any of it. Apparently nobody at all has any faith, not even as much as that tiny mustard seed... Thousands of people pouring forward at our church for healing prayer and their record was O for Thousands of hopefuls... nobody ever was healed... Well, some of them were eventually healed by modern medicine and simply their bodies healing. Nary a blind person could ever see, wheelchairs were still necessary for those who needed them before, nada...
The story of Jonah... That was nothing but a story to me, but if Miracles could happen, then m'eh... that's a pretty normal sounding "miracle"...
Then there were stories of God's seeming uncaring attitude. When kids come out to mock one of his prophets for his baldness and he gets frustrated and curses them, a bear comes and kills all those kids? Really? I thought it said God is love, how is that love?
I can go on and on. So many of these discrepancies between what I saw and what I read/heard led me to just flat tell the people at the church and my mother that i simply didn't believe sometime around 9 years old. Which was a mistake, but that's a whole different story for a different time.