[{"HomeTeam":"A","AwayTeam":"A","HS":10,"AS":20},{"HomeTeam":"B","AwayTeam":"B","HS":1,"AS":200},{"HomeTeam":"C","AwayTeam":"C","HS":100,"AS":20},{"HomeTeam":"D","AwayTeam":"D","HS":3,"AS":223},{"HomeTeam":"E","AwayTeam":"E","HS":10,"AS":20}]

db.collection.aggregate([{$facet:{HS:[{$group:{_id:"$HomeTeam",shots:{$sum:"$HS"}}}],AS:[{$group:{_id:"$AwayTeam",shots:{$sum:"$AS"}}}]}},{$project:{result:{$concatArrays:["$AS","$HS"]}}},{$unwind:"$result"},{$group:{_id:"$result._id",Totalshots:{$sum:"$result.shots"}}},{$sort:{Totalshots:-1}}])