The first thing to do if you could not find the correct pid to kill was to remove the option to start another process.

If the process was running a certain program or script, change the permissions on it so it can't be executed. Then you at least won't have more and more processes being created while you are trying to find the one process you need to kill.

You simple have to keep a level head - ask yourself
How were all these processes created? How can I stop more processes? How do I find the single process that will stop all of this?

You don't give enough info on your situation - I would think you could have found anyone of the processes and seen the parent pid to kill off. Sometimes that is difficult with the system getting slower and slower because of new processes being created.

Another quick way that may or may not work in your situation is to touch /etc/nologin.

Give more details.