SIGKILL
The bullet: the process never hears this ring — the kernel acts alone.
Every other bell rings for the process; this one rings for the kernel. No handler runs, no cleanup happens: the process simply ceases to exist at the next scheduling opportunity.
That is why -9 is the last resort, not the first: orphaned locks, temporary files nobody deletes, children inherited by init. And there is one case even it cannot solve — processes in uninterruptible sleep (state D, usually stuck I/O) only die when the kernel lets them go.
$ kill 4242
$ kill 4242
$ kill -9 4242
(the third attempt didn't ask: it ordered the kernel)