Shiro Tagami is a tough fighter who has been around the block a few times but he is definitely outmatched here against Ikki. Phoenix Ikki was more powerful than Shiro even back when he was a villain during the very early days of Saint Seiya. He’s grown to be millions of times more powerful since then so when you take all of that into perspective then Shiro is really doomed here. Shiro isn’t meant to fight guys who can destroy entire galaxies and it’s hard to get around that. Phoenix Ikki wins.