After 37 tries, Lingering Will finally goes down. Surprisingly, him spamming his desperation move was a good thing. If you can block it he's wide open.
The biggest thing is learning his AI. If you know the signs for what he's going to attack with, they're much easier to avoid. Although in his second phase, he attacks so fast that he is nearly unpredictable so you really have to know what you're doing at that point.
See I didn't even get past the first lifebar. He was going crazy fast, so I had no idea. I'm just saying, at level 99 with the Ultima Weapon, I shouldn't be crying laughing because I got my ass busted, lmao.