[{hero__marvel__avangers:{name:"Iron Man"},hero__marvel__xmen:{name:"X Man"},hhero__dc__justic_leage:{name:"Bat man"}}]

db.collection.aggregate([{$project:{array:{$objectToArray:"$$ROOT"}}},{$unwind:"$array"},{$match:{"array.k":{$regex:".*marvel.*",$options:"i"}}},{$replaceRoot:{newRoot:{$arrayToObject:[["$array"]]}}}])