Comparing values in columns and showing difference

[RyanHare92]

Hi,

I have two columns, each one of them has a list in each row of certain values. I want to compare the two columns and show which values in the second column are not present in the first. The following is an exaple:

I have managed to do this in Power Query, but I find it very messy. I've spent hours now trying to create a calculated column to do this, but I've had no success. 

[ThxAlot · Accepted solution]

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjDUMTDSMTBW0oExTZRidYDiIJaOgSlIHCSvY2CmFBsLAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t]),
    #"Added Diff" = Table.AddColumn(Source, "Diff", each Text.Combine(List.Difference(Text.Split([Column2],","), Text.Split([Column1],",")),","))
in
    #"Added Diff"

[RyanHare92]

Update:

I'm very close. So far, this is what I have:

New =

VAR FirstList =

    IF(Candidates[old_components] = "-", BLANK(), Candidates[old_components] & ",")

VAR SecondList =

    IF(Candidates[new_components] = "-", BLANK(), SUBSTITUTE(Candidates[new_components] & ",", " ", ""))

VAR UniqueValues =

    CALCULATE(

        CONCATENATEX(

            GENERATESERIES(1, LEN(SecondList), 3),

            VAR CurrentValueIndex = [Value]

            VAR CurrentValue = TRIM(MID(SecondList, CurrentValueIndex, FIND(",", SecondList, CurrentValueIndex) - CurrentValueIndex))

            RETURN

                IF(

                    len(CurrentValue) <> 2,

                    BLANK(),

                    if(

                        ISBLANK(SEARCH(CurrentValue & ",", FirstList, 1, BLANK())),

                        CurrentValue,

                        BLANK()

                    )

                ),

            ", "

        )

    )

RETURN

    SUBSTITUTE(UniqueValues, ", ,", "")

The only issue I'm having now is that it's concatenating a bunch of blank values. I need to find a way of not concatenating the value if the current value's length is smaller than 2, or a good way to clean up the result to get rid of the excess commas.