What does the word 「ぶっぱたく」 mean?

Question

A little girl who said the following sentence holding a geta in her hand is angry that officers not allow her and her friends to go inside a place.

ひいきしやがるとぶっぱたくぞっ。

Answer 1

This is the prefix ぶっ (deriving from 打つ【ぶつ】) applied to the verb はたく (叩く) "to knock/hit". (For details, see your other question about ぶったてる.)