What was it that finally made you feel confident in calling yourself 100% atheist?

My question here is about a final, big thing that "put the final nail in the coffin" for religion in your eyes. My parents are Anglican Christians from the UK and are very moderate, so our household was never overbearing. However, even as a child, I thought that religion didn't make much sense. This is, of course, not to disrespect my parents' beliefs. I had a very good upbringing luckily, although I accept that makes me quite privileged and that most people here probably didn't have that luck with religious parents.

Anyway, during my childhood, people often remarked that I asked a lot of questions, particularly about religion. It was more out of both curiosity and confusion rather than to challenge anyone (the "challenging people" was more common during my teenage years). However, I definitely had some teachers back then who hated it and I also remember a priest not knowing how to deal with me! I was very inquisitive, basically. I just couldn't understand how so many awful things happened in this world supposedly created by an omnipresent, omnipotent, and omnibenevolent deity. Even my parents were never truly able to answer my questions. I didn't think about it too often though until I became a teenager.

I went to Church of England high school in London that loved to mention Christianity every chance they got. While our Christian schools are generally not as bad as the ones in the United States, they can still be very preachy. RE (religious education) classes worst the worst, naturally. It wasn't quite the more extreme, hateful anti-atheist rhetoric you see in some other countries, but they clearly didn't take kindly to young, free thinking minds. Some of them were nice, but even then, none of the teachers were ever able to quite answer my questions. My questions weren't just about bad things happening either, I also asked about the "something from nothing" argument. Many Christians will tell you that, if someone can't come from nothing, then the Universe must've had a cause (that cause being "God"). However, my counterargument was always that "God" himself must've also come from something. So, not only does this all powerful, all knowing, and all loving deity somehow not have the ability or will to strike down evil people, he also apparently just appeared into existence one day. How does that make any sense?

The fact that no Christians could really answer me properly or at least give me satisfying answers continues to this day. I think that it's probably the main reason I feel confident in calling myself an atheist. Atheists are actually able to give me proper answers and I've seen them even give good answers to doubtful atheists and agnostics, who can't help but wonder about the "something from nothing" argument. There's actually an interesting theory that there will be another big bang after the Universe completely dies and that it's possibly been happening repeatedly. Whatever started the chain reaction is a mystery, but I find more answers from atheists and science than I do with religion. I'm now an adult, but I've met far more atheists who are able to have these conversations, listen, and even question their own beliefs.

One topic I've been very interested in recently is human evolution, which is another thing that pushed me further towards atheism, as it contradicts all the Abrahamic religions' creation stories. What's actually quite hilarious is there are now Christians admitting that neanderthals existed but were actually homo sapiens despite all the evidence of the contrary! They were very close to us but they weren't the same. A funny thought I also just had it what if religious neanderthals were saying the same about us? Now that would be quite funny!