How powerful is Pie Xie Jian Fa ?

[Trien Chieu]

So can Taiji Sword defeat BXJF ?

Absolutely. Chongxu's Taiji Swordplay would easily defeat Lin Pingzhi's BXJF. Taiji Sword may not be as great as DG9S, it's still among the very best martial art. It's still the martial art for the heroes/winners whereas BXJF/KHBD is the martial art for the sore losers.