Mac. No Crtl-Alt-Del available.
Command-Space bar to use Spotlight
Type in Activity Monitor
There is is Activity Monitor in your Utilities folder in your Applications folder. It does more that the Windows Ctrl-Alt-Del. You can see whats running, whats using CPU time, network access, and a lot more. You can sample what data is being processed at the moment. . . and quit processes or applications.
You can also use force quit without invoking that. If you get something that hijacks the browser, force quit, the restart the browser while holding the Shift key. That starts Safari with a clean slate.