[{"_id":ObjectId("100000000000000000000000"),"from":ObjectId("100000000000000000000000"),"to":ObjectId("200000000000000000000000"),"date":ISODate("2021-09-03T11:23:25.184Z"),"messageContent":"111"},{"_id":ObjectId("200000000000000000000000"),"from":ObjectId("200000000000000000000000"),"to":ObjectId("100000000000000000000000"),"date":ISODate("2021-09-02T11:23:25.184Z"),"messageContent":"222"},{"_id":ObjectId("300000000000000000000000"),"from":ObjectId("300000000000000000000000"),"to":ObjectId("100000000000000000000000"),"date":ISODate("2021-09-04T11:23:25.184Z"),"messageContent":"333"},{"_id":ObjectId("400000000000000000000000"),"from":ObjectId("300000000000000000000000"),"to":ObjectId("400000000000000000000000"),"date":ISODate("2021-09-05T11:23:25.184Z"),"messageContent":"444"}]

db.collection.aggregate([{$match:{"$or":[{"from":ObjectId("100000000000000000000000")},{"to":ObjectId("100000000000000000000000")}]}},{$project:{whom:{$first:{$filter:{input:["$from","$to"],as:"i",cond:{$ne:["$$i",ObjectId("100000000000000000000000")]}}}},date:1,messageContent:1,to:1,from:1}},{$sort:{"date":-1}},{$group:{_id:"$whom",date:{"$first":"$date"},message:{"$first":"$messageContent"},to:{"$first":"$to"},from:{"$first":"$from"}}}])