[{"software":"opac","release":"1.0","feature":"xxx","featureVersion":"3.2"},{"software":"opac","release":"1.0","feature":"yyy","featureVersion":"1.2"},{"software":"opac","release":"1.0","feature":"zzz","featureVersion":"8.9"},{"software":"opac","release":"3.0","feature":"xxx","featureVersion":"6.1"},{"software":"opac","release":"3.0","feature":"zzz","featureVersion":"10.0"}]

db.collection.aggregate([{$group:{_id:{feature:"$feature",software:"$software"},data:{$push:{release:"$release",featureVersion:"$featureVersion"}}}},{$match:{data:{$size:2}}},{$project:{_id:0,data:{"$mergeObjects":[{"$arrayToObject":{$map:{input:"$data",in:{k:{$concat:["$_id.software"," ","$$this.release"," featureVersion"]},v:"$$this.featureVersion"}}}},{software:"$_id.software","common feature":"$_id.feature",}]}}},{"$replaceRoot":{"newRoot":"$data"}}])