[{"_id":1,"entity":"Category","property":"name","changed":"2020-08-30"},{"_id":2,"entity":"Category","property":"name","changed":"2020-08-31"},{"_id":3,"entity":"Category","property":"description","changed":"2020-08-29"},{"_id":4,"entity":"Category","property":"description","changed":"2020-08-30"},{"_id":5,"entity":"Category","property":"description","changed":"2020-08-31"},{"_id":6,"entity":"Product","property":"price","changed":"2020-08-20"},{"_id":7,"entity":"Product","property":"price","changed":"2020-08-31"}]

db.collection.aggregate([{$match:{}},{$sort:{changed:-1}},{$group:{_id:{property:"$property",entity:"$entity"},document:{$first:"$$ROOT"}}},{$replaceRoot:{newRoot:"$document"}}])