While Workfront does not currently offer an exclusive Report for the Critical Path, you can easily create a Task Report that displays the needed information.
- Navigate to Reporting Tab
- Select the option "+New Report"
- Create a Task Report
- Add the Filter, "Task>>Is Critical"
As an added benefit, you may want to add a Prompt to the Report so that you can easily pull in the Critical tasks for a given Project. Please see Working with Prompts for steps on how you can setup your Report with a Prompt.