[{"myLocalizedField":{"en":"Hello world","de":"Hallo Welt","cz":"Ahoj světe","es":"Hola Mundo"}},{"myLocalizedField":{"en":"There is no one who loves pain itself, who seeks after it and wants to have it, simply because it is pain...","de":"Da ist niemand der den Schmerz an sich liebt, der danach sucht und ihn haben möchte, einfach weil es Schmerz ist...","cz":"Nikdo nemiluje bolest samu, nevyhledává ji, ani ji nechce získat, protože bolest...","es":"No hay nadie que ame el dolor mismo, que lo busque, lo encuentre y lo quiera, simplemente porque es el dolor."}}]

db.collection.aggregate([{"$addFields":{"tmp":{"$objectToArray":"$myLocalizedField"}}},{$match:{"tmp.v":{$regex:"llo"}}},{$unwind:{path:"$tmp"}},{$match:{"tmp.v":{$regex:"llo"}}}])