Tales of Symphonia

My party keeps getting clobbered xD

my characters levels range from 14-22.......so am I underpowered or is there a "key" to beating him

Here's a strategy I've read on gamefaqs, hope it helps !

"The Windmaster has one special attack. The Windmaster spins towards the
target, swinging the scythe attached to it's lower section. This move
is more powerful than the Adulocia's bubbles, so be more careful. The
magic attack is Wind Blade, which isn't really anything to worry about.
Use a party of Lloyd, Genis, Raine, and Kratos. Lloyd should do his
typical combo + Tetra Slash, Genis should cast anything but Wind magic,
Raine should heal, and Kratos should do what Lloyd and Raine do: attack
and heal. This battle really isn't any harder than the
Adulocia/Amphitra battle."