In the event a pipeline build will not die you can hard kill it - however hard killing it will leave the JVMs CPS thread still running on the master.
e.g. with the script
you will need to hard kill it to stop it (on windows at least) - but inspecting the JVM threads you can see the CPS thread is still running in a tight loop.
A hard kill should probably (if it is safe without causing deadlocks elsewhere) brutally kill the thread as well. After a while you may run out of handles or other native resources due to the thread usage, meaning you need to restart Jenkins to get it working again.