Database
[{"_id":ObjectId("623a92139e19f99295167786"),"headline":"headline1","comments":[{"userID":ObjectId("623a7b199e19f99295167776"),"time":ISODate("2022-03-24T10:20:23Z")},{"userID":ObjectId("623a7b199e19f99295167776"),"time":ISODate("2022-03-25T10:20:23Z")},]},{"_id":ObjectId("623be3ce9e19f99295167787"),"headline":"headline2","comments":[]}]
Query
db.collection.aggregate([{$match:{_id:ObjectId("623be3ce9e19f99295167787")}},{$unwind:{path:"$comments",preserveNullAndEmptyArrays:true}},{$sort:{"comments.time":-1}},{$group:{_id:"$_id",headline:{$first:"$headline"},comments:{$push:"$comments"}}}])