[{"_id":ObjectId("5e43924a12f90430cc92f788"),"score":1.0,"value":10.0},{"_id":ObjectId("5e43924a12f90430cc92f789"),"score":3.0,"value":10.0},{"_id":ObjectId("5e43924a12f90430cc92f78a"),"score":1.0,"value":10.0},{"_id":ObjectId("5e43924a12f90430cc92f78b"),"score":4.0,"value":10.0},{"_id":ObjectId("5e43924a12f90430cc92f78c"),"score":1.0,"value":10.0},{"_id":ObjectId("5e43924a12f90430cc92f78d"),"score":5.0,"value":10.0},{"_id":ObjectId("5e43924a12f90430cc92f78e"),"score":5.0,"value":10.0},{"_id":ObjectId("5e43924a12f90430cc92f78f"),"score":10.0,"value":10.0}]

db.collection.aggregate([{$group:{_id:"$score",avg:{$avg:"$value"}}},{$group:{_id:"",min:{$min:"$_id"},max:{$max:"$_id"},data:{$push:"$$ROOT"}}},{$project:{_id:0,data:1,nums:{$range:["$min","$max",1]}}},{$project:{data:{$concatArrays:["$data",{$map:{input:{$setDifference:["$nums","$data._id"]},in:{_id:"$$this",avg:0}}}]}}},{$unwind:"$data"},{$replaceRoot:{newRoot:"$data"}}])