killall5 -9 # If all options fails this is the last option
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
sudo kill -9 process_id
ps -ax | grep application name
Go to System Monitor
Search for process name
Click End Process