regexp

re="\(([^()]|(?R))*\)"
array=(
    "[macdoll(マコ(・c_・))]shutter chance!!(ラブライブ)"
    "[しろむじ(ん坊主)]まる限定。((G)えでぃしょん)"
    "[PASTEL WING(如月あいす)]アイスフレンド(嫁)03(ガール(仮))"
    "x(1)x((2)2)(3(33))x((4((44))))x"
)

for s in "${array[@]}"
do
    echo $s
    echo ---
    echo $s | grep -Po $re
    echo
done