Quartus II: Where are the worst-case paths?
It's non-obvious how to use the QuartusII built in reports. You need to start from the page Multicorner Timing Analysis Summary and look down the right hand side looking for any setup, hold, recovery or removal slacks that are negative. Once you find the failing clock and type of failure (setup, hold) you can hunt around for the details in other sections. As a guide: setup/recovery failures are (usually) found in the slow/hot model, and hold/removal failures are uncovered when testing at the fast/cold corner. 

Generally I ignore the reports built into Quartus and do timing analysis in the seperate TimeQuest Timing Analyser GUI. Launch it from Quartus by double clicking TimeQuest Timing Analyzer under Timequest Timing Anaysis in the Quartus "Task" view or by hitting the stopwatch on the toolbar.

There are many ways to drive this tool. One way is to list all the design clocks by double clicking Reports -&gt; Slack -&gt; Report Setup Summary, then right click on the clock of interest and choose Report Timing.... The clock section is pre-filled out and ignore the other fields, so just hit the "Report Timing" button. You will get a Summary of Paths screen showing the most critical slacks by path. From here you can chase through to either Chip Planner for routed view, or back to RTL/Technology viewer to look at source. Note the most critical model is selected depending on the report type.

If you have any non-zero counts on the Unconstrained Paths section the tools will complain. It takes a few hours to go through and properly constrain board signals but worth cleaning it up.