[{"empno":6000,"points":80},{"empno":5000,"points":60},{"empno":7000,"points":70},{"empno":6000,"points":60}]

db.collection.aggregate([{"$match":{"empno":{"$eq":6000}}},{"$group":{"_id":null,"max-points":{"$max":"$points"}}},{"$project":{"_id":0,"max-points":1}}])