Remove duplicates with multiple criteria

I think you basically want to group by User ID and Course Title (or whatever course identifier is) and then grab the top row in your group where you've sorted the table beforehand to ensure that the top row is the one you want to represent the User/Course pair.

let
    // dummy data provided
    Source = Table.FromRows(
        Json.Document(Binary.Decompress(Binary.FromText("xdNPa8MgFADwryKeNshBTf/tmK0pZCzrwY4dSg42fayBVMPTFPLtp250p0EHaXd56lP0h0+3WyqYYDShOUtZyvnMd5dZCODD01qWGSm0A9TKNUar1mc558Q3p+JlE9aYY9eCC8sz7RqHvXUktxb8QLXWp0uj92pISNZh05JpQvyR3OffJK2SWwDeYa/BRsOrOcFxB0jE5PaOzaHHL8YKdtgrHAifR4YYj1Ho+hoXMp34rqxjOPzL07iu4FnpWJCURUQ6IuKSikjleowQCZ37rsj493EJZYVNhKxrZyJD/MoQgj3MwkTY+9GETUv1oRWRDgb0I3K3mPP7v53/80vOgsVZsMxpVX0C", BinaryEncoding.Base64), Compression.Deflate)), 
        let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Target Year" = _t, #"User ID" = _t, #"First Name" = _t, #"Last Name" = _t, Group = _t, Division = _t, #"Course Type" = _t, #"Completion Status" = _t, #"Course Title" = _t, #"Assignment Date" = _t, #"Country/Region" = _t]
    ),

    // need this step if we actually want date sort later on to be correct
    Types = Table.TransformColumnTypes(Source,{{"Assignment Date", type date}}),

    // we will use GroupKind.Local later, so sort everything first
    SortRows = Table.Sort(
        Types,
        {
            // first sort by your group key (User ID and Course Title)
            {"User ID", Order.Ascending}, {"Course Title", Order.Ascending},
            
            // then sort so representative row is first
            // {Complete before Incomplete}    and    {newer before older }
            {"Completion Status", Order.Ascending}, {"Assignment Date", Order.Descending}
        }
    ),

    // specify group columns and then dynamically get the rest of your columns
    GroupByCols = {"User ID", "Course Title"}, ExpandCols = List.Difference( Table.ColumnNames( Types ), GroupByCols ),

    // now do the local grouping where you grab your top row
    Group = Table.Group(
        SortRows, 
        GroupByCols, 
        {{"rows", each Table.First( _ ) , Type.TableRow( Value.Type( SortRows ) ) }},
        GroupKind.Local
    ),

    // expand to restore all your columns
    // Note: this should be manual if you want a subset of cols and you can remove ExpandCols step
    ExpandRows = Table.ExpandRecordColumn(Group, "rows", ExpandCols )
in
    ExpandRows

Result: