to a ... degree 是英语中的惯用表达，意思是“到……程度”，to a superhuman degree 的意思是“达到了超乎常人的程度”，结合前文的mastered the martial arts（精通武术），故可理解为“身怀绝世武功”（即精通武术达到了超乎常人的程度）。类似的例子如：
(1) I agree with you to a certain degree. 我在某种程度上同意你的意见。
(2) He taught himself to carve to a high degree of proficiency. 他自学雕刻达到了很高的水平。
(3) The boss sometimes follows her instincts to a dangerous degree. 老板凭她的直觉做事，有时达到危险程度。
(4) The number of terrorist attacks has increased to a terrifying degree. 恐怖分子袭击的次数已经达到了骇人的程度。
(5) The tax changes will especially hit those on high incomes and, to a lesser degree, small businesses. 税收政策的变动对高收入者影响尤甚，对小企业的影响相对较小。