By force quit, if you mean killing an app then use the kill command and the app PID.
Top will show you whats running and the PID
PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND
591 user 96 0 142M 15800K select 0:10 0.29% 0.29% Xorg
617 user 20 0 62008K 54012K kserel 0:56 0.00% 0.00% firefox-bin
594 user 96 0 5676K 5020K select 0:01 0.00% 0.00% fluxbox
will kill firefox in the example above.
If you want to kill the OS then use the halt command.
To run lisa if it is installed just su to root then type lisa.
You should not be running a GUI as root, bad idea. If you need root access to a file or process just su to root and run it. Or better yet, set up your sudoers file then a user can run commands as root.