For me, Ruby Weapon really stands out. I had a save once where I stumbled into a materia configuration that let me trigger the All Lucky Sevens by adding in a level 1 HP +10%, so I went into the fight thinking it would make it a piece of cake. Boy was I wrong A humbling and challenging experience.

Last week my gf and I did a video on our YT channel about our favorite FF bosses. Here's the video if anyone's interested:

https://www.youtube.com/watch?v=CSqdMuAUefE