[{id:"1234567890",answers:[{id:111,deleted:0},{id:222,deleted:0},{id:333,deleted:1},{id:444,deleted:1}]},{id:"0987654321",answers:[{id:111,deleted:0},{id:222,deleted:1},{id:333,deleted:1}]}]

db.collection.aggregate([{$match:{id:"1234567890"}},{"$unwind":{path:"$answers"}},{$match:{"answers.deleted":1}},{$group:{_id:"$id",answers:{$push:"$answers"},allFields:{$first:"$$ROOT"}}},{"$replaceRoot":{"newRoot":{"$mergeObjects":["$allFields",{"answers":"$answers"}]}}}])