Other man made disasters that haunt you besides 9/11?

Today, I was thinking about the tragedies that surrounds 9/11 and how it haunts me. This made a question pop into my mind. The question is: what other man made tragedies haunt you like 9/11 does? For me, it is the Station Night Club fire. I would love to hear your responses.

Note: I know this sub is for archiving 9/11. If this post does not fit here, please let me know and I will remove it immediately. Thank you!