While the GUI (SSMS) has UNLIMITED in there, that’s actually not the right answer here. If you set the truncation log file to UNLIMITED and click save, it’ll actually reset the maximum file size to 2TB, since that’s actually the max supported size of a transaction log file.
So how to do create a single transaction bigger than 2 TB? You have multiple transaction log files. Also, don’t create 2TB transactions. If those fail, rollback is going to take a LONG time.