Well, kind of. Lugh Beowulf is a nature spirit (on par with a True Ancestor) and nigh immortal. Soujuurou didn't kill him, but rather forced the sensation of dieing on him. He introduced the feeling of dieing to an immortal being who had never so much as suffered defeat before. The experience left him a quivering, petrified mess, and the idea of experiencing it again left him with an overwhelming fear of Soujuurou.