Context: bad guy triggers protagonist by saying taboo word.
yowattenakereba hontou {kateru} aite demonai-n-daga na 弱ってなければ本当勝てる相手でもないんだがな If [she] weren't weakened in reality [she] wouldn't be an opponent [that] {[I] could defeat}.
kateru 勝てる (potential verb.) To be able to win against [someone]. To be able to defeat [someone].