ShinyCharizard said:
Yeah if you've got some advice for me I'm more than happy to take it on board. It will be awhile before I attempt him again though. I've got the HD remake but I haven't got far into it yet.
For the original Kingdom Hearts 1, there are a few things you can use. For one, get the Ribbon, as it not only buffs all resistances to elements by 20%, it raises defense by 3. Then try to stack the dark resistance, as Sephiroth's attacks are considered dark element. Another thing is Sephiroth's Heartless Angel move, the one that cause you to lose all magic and health down to one. He has a windup for that, and if you manage to hit him during it, he will instantly teleport behind you. If he does get it off on you, he will also always teleport behind you, so dodge roll or guarding helps. To interrupt Heartless Angel it also helps to have Strike Raid because you actually have invincibility frames while using it.
For Final Mix, it's a bit easier to manage because of some new abilities added into Final Mix that weren't in the first game. For one, Leaf Bracer helps since you have invincibility frames when casting cure on yourself, so timing it right helps. Another ability that helps is Slapshot, which can be abused to negate half of Sephiroth's attacks because of the constant and quick attacking you do. Finally, Sliding Dash helps you get closer to Sephiroth for Heartless Angel.
Now you need to keep in mind, Sephiroth will vocally use Heartless Angel for a while, but when close to death, he won't vocally say it any more, so always keep a lock onto Sephiroth. Using Aeroga helps lower the damage you take as well, so it helps to keep it constantly cast on yourself. And stack all your items with just Elixirs, as using Mega Elixirs would be a waste.
Hope this helps.