The Greek idiom of the headword phrase is difficult to translate. Literally, kaka\ kakw=n meaning "evil things of evil things". The effect seems to be one of intensification, e.g. English "wonder of wonders".
[1] Diocles fr. 2 Kock (and K.-A.); cf. however delta 1155, which suggests that the title of this play was plural Bacchae (rather than singular Baccha as here).
[2] For plu/nw in this sort of sense see LSJ s.v. II, citing the present instance among others: web address 1 below. Note however, that there, and conventionally elsewhere, the line is read "and he will give you..." (i.e. dividing plunei= te rather than plunei=te).