The equivalent of Control-Alt-Delete on a Mac for force quitting frozen apps is Option-Command-Esc.
When you press the Control-Alt-Delete keys on a Windows PC, you'll be given the options to lock your screen, switch users, sign out of your account, change a password, and access Task Manager. Among these, terminating unresponsive apps in Task Manager is the most popular usage of the Control-Alt-Delete keys.
However, the same combination does nothing on a Mac. To force quit an unresponsive app on Mac, you can use the Option-Command-Esc keys to activate the "Force Quit Applications" window, then choose the frozen app and click "Force Quit."