What tool do you want?
List Comparison similar to http://www.listdiff.com/

Describe the solution you'd like
Two fields, where you paste two lists
The output would be items in A that are not in B, Items in both A & B, and items in B not in A
Could also show a complete list of items in A and B without duplicates

Is their example of this tool in the wild?
http://www.listdiff.com/

Additional context
This is similar to the Text Diff, but the Text Diff will show "x-ad" and "x" to be similar, but the comparison above would compare complete lines.