Because I have that kind of time, I've made a weapon weakness chart for the final boss.Phase 1
21 Hits - Hard Knuckle, Pharaoh Shot Lv. 3*, Ballade Cracker*
11 Hits - Atomic Fire Lv. 3* (may pierce for up to 3 hits!)
No damage - Everything else
* = Will need to refill this weapon.
Phase 2
1 Hit - Top Spin
No damage - Everything else
Both Phases
Leaf Shield (worn version only) comically throws him into the ceiling (for no damage), but makes him impossible to actually defeat.
The best way to deal with the final boss might be to do some critical damage with the Atomic Fire, then fire Hard Knuckles as fast as robotically possible. As others have said, aim for above his head and you should hit him more often than not. After that, it's a relatively simple matter of using Rush Coil to hop up to his level and Top Spin him into oblivion.