Source Result
ColumnA ColumnB Data1 Data2 ColumnA NotMatchB Data1 Data2
USNTS USNTS ABC
123
USNTS USSPZ ABC
123
USNTS USSPZ ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USNTS USLVV ABC
123
USLVV USNYC ABC
123
USMSY USMSY ABC
123
USHOU USHOU ABC
123
USMSY USMSY ABC
123
USMSY USMSY ABC
123
USLVV USNYC ABC
123
USNYC USNYC ABC
123


Code:
// Table1
let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    Diff = Table.AddColumn(Source, "NotMatchB", each List.Difference({[ColumnB]},{[ColumnA]})),
    Expand = Table.ExpandListColumn(Diff, "NotMatchB"),
    Filter = Table.SelectRows(Expand, each ([NotMatchB] <> null)),
    TSC = Table.SelectColumns(Filter,{"ColumnA", "NotMatchB", "Data1", "Data2"})
in
    TSC