1st round goes to Graf. He fights player gears on foot on a moving spacecraft. He can teleport and can theoretically do what Id can do... and that's tk-like energy holds. He's also faster and more durable than Sephiroth. Flight from Sephiroth would be minor annoyance
2nd round: You kidding me? Alpha Weltall withstood a district leveling explosion from a battle cruiser holding high yield explosives, curbstomp omnigears (those gears that are stronger than 1000 gears, and can destroy cities with a wave of their hands), and didn't get outright beaten by just awakened Xenogears. Seraph Sephiroth doesn't have much in the way of cutscenes working for him, but I can imagine that he's not winning against someone who'd curbstomp the entire team that beat him.