Due to a problem in the Quartus® Prime software version 15.1 and earlier, you may see the TimeQuest™ Timing Analyzer freeze when you run the report_timing report and there is a large total negative slack (TNS).
To work around this problem, run report_timing without clock path reporting. Use "-detail path_only" instead of "-detail full_path" in the report_timing command.
If you are using the GUI, in the Report Timing windows, click on the Detail level dropdown menu under Output section, select Path only and click Report Timing.
This problem is scheduled to be fixed in a future release of the Quartus Prime software.