Marke duplicated base on other column

Here is an example of one way to accomplish this...

let
    Source = 
    Table.FromRows(
        Json.Document(
            Binary.Decompress(
                Binary.FromText(
                    "i45WclTSUTJSitWBsIzRWE5AlikayxnIMgSzXIAsEzgLKBsLAA==", 
                    BinaryEncoding.Base64
                ), 
                Compression.Deflate
            )
        ), 
        let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Criteria1 = _t, Criteria2 = _t]
    ),
    #"Changed Type" = 
    Table.TransformColumnTypes(
        Source,
        {{"Criteria1", type text}, {"Criteria2", type text}}
    ),
    Custom1 = 
    Table.AddColumn(
        #"Changed Type", 
        "_mark", 
        each 
        if List.Count(Table.SelectRows(#"Changed Type", (x)=> x[Criteria1] = [Criteria1])[Criteria1]) = 1
            then 1
            else if List.Count(Table.SelectRows(#"Changed Type", (x)=> x[Criteria1] = [Criteria1])[Criteria1]) = 2 and List.Count(Table.SelectRows(#"Changed Type", (x)=> x[Criteria2] = [Criteria2] and x[Criteria1] = [Criteria1])[Criteria2]) = 2
                then 2
                else if List.Count(Table.SelectRows(#"Changed Type", (x)=> x[Criteria1] = [Criteria1])[Criteria1]) = 2 and List.Count(Table.SelectRows(#"Changed Type", (x)=> x[Criteria2] = [Criteria2] and x[Criteria1] = [Criteria1])[Criteria2]) <> 2
                    then 8
                    else if List.Count(Table.SelectRows(#"Changed Type", (x)=> x[Criteria1] = [Criteria1])[Criteria1]) > 2
                then 3
                else 9
    )
in
    Custom1