The meaning of のに is "despite", "although".
But in the sentence, it seems to have another role. Could you explain?
Context: another character wants to join the team consisting of the protagonist and Aqua.
俺はここ二回のカエルと戦いで、どうもこの女神、ちっとも使えないんじゃないかと疑っているのだ。 はっきり言って、アクア一人でも厄介なのにこれ以上問題児は。。。
Our recent battles with the Giant Toads had left me doubting whether this goddess was going to be any help to me at all. To be blunt, Aqua was a liability all by herself. To take on another problem child ...