Everyone is wrong !
I have the right awnser it has to be Sephiroth whit the short hair no one would be that leet whit a sword other then him.
And notice how in the trailer they show it in that order.
Lifestream , battle whit short hair sephiroth, short hair sephiroth bow down in front of Jenova (probably Jenova), Then probably a memory of the past.