[{_id:1,kills:12,deaths:6,assists:1},{_id:2,kills:2,deaths:2,assists:22},{_id:3,kills:1,deaths:2,assists:3},{_id:4,kills:0,deaths:23,assists:4},{_id:5,kills:6,deaths:3,assists:5},{_id:6,kills:7,deaths:1,assists:6}]

db.collection.aggregate([{$group:{_id:null,maxKills:{$max:"$kills"},maxDeaths:{$max:"$deaths"},maxAssists:{$max:"$assists"},docs:{$push:"$$ROOT"}}},{$project:{_id:0,maxKills:{$arrayElemAt:[{$filter:{input:"$docs",cond:{$eq:["$$this.kills","$maxKills"]}}},0]},maxDeaths:{$arrayElemAt:[{$filter:{input:"$docs",cond:{$eq:["$$this.deaths","$maxDeaths"]}}},0]},maxAssists:{$arrayElemAt:[{$filter:{input:"$docs",cond:{$eq:["$$this.assists","$maxAssists"]}}},0]}}}])