Sorry, but Genesis is somewhat of a sore spot for me.
He's such a poorly written character, he felt awkwardly thrust into moments that worked better without him, his character felt like it was falling flat in what it was trying to do, he lacked chemistry with other characters, he wasn't intimidating as a villain, his dialogue gave me second hand embarrassment, he wasn't thought provoking at all.
Even the creator's intent with him is so unclear, we've spent an entire long thread trying to figure out if he was a creator's woobie pet that we were meant to sympathize with, or purposely irritating. And even when he was suppose to be irritating, I believe it wouldn't be like the way he frustrated me as a player, where I was so annoyed at all his screentime I was aggressively mashing x to skip his dialogue rather than a "Shush you villain!" type of feel. It felt like he took away from each scene more than he added. Repetition CAN work for dialogue, but here it was just boring at best and pretentious at worst.
The Reactor scene is the one that most people talk about but I feel like it's just the worst example of a bigger problem, the plot centering around Genesis was boring to play through and there was better time spent elsewhere. I absolutely loved Crisis Core. But it was best when it was a character piece, focusing on Zack and his relationships with the people around him, and his slow realization of the corruption in Shinra and the loss of his dreams. Genesis was a part of it, but easily the worst part and I feel as if he could have been written out, and with time the story would have been better for it.
An interview once said (I can't find the source anymore) that there was once plans to make more story about Zack and Cloud's trip to Midgar. That would have been amazing, but no... have some more Genesis monologuing about some other stupid shit.
Then at the very last of the game you realize his dream is to hurrr eat dumbaples with his frendz and he gets to see the goddess is completely cured with the woobie look on his face is cured and at the end of DoC he goes on about work to be done- which apparently is about saving the world. Give me a fucking break.
...
But yeah his sword is pretty cool.