Removing duplicates with MAX condition in powerquery

See the working here - Open a blank query - Home - Advanced Editor - Remove everything from there and paste the below code to test (later on when you use the query on your dataset, you will have to change the source appropriately. If you have columns other than these, then delete Changed type step and do a Changed type for complete table from UI again)

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WsrQwVNJRigJiY30TfSMDIwMgE0oZQpmGSrE60UqGRsZAvhNITN/QGKTUEJdSE1MzID8YiE30TYkw1AVsvSERKl3BZlrgVQnxUjhCJQF3uoPECdgOUekBNtMIpNIIv0pPiJl4PB8LAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"PO IMPORTER" = _t, Attribute = _t, #"LI APPROVAL DATE" = _t, Year = _t, Quarter = _t, YearMerged = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"PO IMPORTER", Int64.Type}, {"Attribute", type text}, {"LI APPROVAL DATE", type date}, {"Year", Int64.Type}, {"Quarter", Int64.Type}, {"YearMerged", Int64.Type}}),
    #"Sorted Rows" = Table.Sort(#"Changed Type",{{"PO IMPORTER", Order.Ascending}, {"LI APPROVAL DATE", Order.Descending}}),
    BuffTbl = Table.Buffer(#"Sorted Rows"),
    #"Removed Duplicates" = Table.Distinct(BuffTbl, {"PO IMPORTER"})
in
    #"Removed Duplicates"