I beat him at lvl 47 and I used only 1 elixir fighting him.
Here are some tips
if this is wrong for the forum just delete it )
This is how i beat him
First 5 Bars :
Normal ground attacks,Air attacks and the skill that reduce your hp until 1
In this stage It's best to not get damaged by sephiroth by keeping him ground based attacks.When he starts to attack Double Jump then attack him when he is finish attacking.
Next 5 bars :
(same as first stage) + Magic balls,Dark Sin, and i think it's hell fire
This is the hard part.Be sure to have Full MP.He will starting using dark magic balls around you.Use reflectga as fast as possible.Continue,sometimes later when you are close enough to him he will use Hell fire that will suck you to him and gives damage.RUN !!!Then it is either he will use dark sin(takes out your hp and mp)Lock on and and double jump then attack him OR you could use Trinity(limit)
Last 5 bars :
He glows purple.This should be the tense part.He will cast a LOT of dark balls around you and then he will quickly hits you.Use reflectga when he starts moving after casting.Attack,attack,attack.He will use Meteor Rain on you(this is easy).Keep double jump to left and right.Then you'll know what to do
Is this a spoiler?