Power Query delete row if value found in another column

Try this:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSUVKK1YlWMoIxjGEMEyDDEMwyBbKMlWJjAQ==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"ID A" = _t, #"ID B" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID A", Int64.Type}, {"ID B", Int64.Type}}),
    #"Merged Queries" = Table.NestedJoin(#"Changed Type", {"ID A"}, #"Changed Type", {"ID B"}, "Changed Type", JoinKind.LeftAnti),
    #"Removed Columns" = Table.RemoveColumns(#"Merged Queries",{"Changed Type"})
in
    #"Removed Columns"

Input:

Output:

Explanation:

You are joining back to the same table you are in and do the left anti.

Hope this helps!