ubuntu force kill application code example

Example 1: how to force quit application in ubuntu

One way is to hit alt+f2, then type xkill and hit enter. 
Now click on the program you would like to force quit.

Example 2: ubuntu kill process

pidof slack 
9734 9718 9716 9708 9622 9619
sudo kill -9 process_id

pidof apt 
9734 9718 9716 9708 9622 9619
sudo kill -9 9734 9718 9716 9708 9622 9619

Example 3: kill process ubuntu

sudo kill -9 process_id