Here's a devestaing way to lower enemy HP i'll tell you firstly when you have ultima weapon and are at max level using all the str sources you can get on cloud have 2 mastered 2x's materias yeah it takes awhie but it's damn worth it and 1 mastered counter materia now on a joined solt have the mastered 2x's cut paired with counter attack and have a normal mastered 2x's cut anyhwere you see fit now then cloud is attacked he'll counter with the 4x's cut dealing 9,999 per hit by the time he's finished you should be able to enter commands again then have him attack normally with 4x's cut that's a total of 8 hits in a row doing 9,999 on all hits that's devestaing and when cloud dies a special bonus a mastered final attack paired with pheonix mastered but the 8 hits in a row you'll nearly be doing as much as 99,999 it's good but does take time and it makes emerald weapon the easiest boss ever fought and midgar zolem dies in a hit at that point.
here's a good tip be greviously overlevelled when your there as in level 35 i was and kicked the crap out of everything that crossed me but if you have a life then don't do that it took me close to 30hrs so there you have it.