I tried kill -9 698
but the process did not die.
$ ps -ef | grep chromium
502 698 811 0 0:01.24 ?? 0:07.28 /Users/lucius/chromium/
Given the path to your program, I assume you're currently running this under Xcode, and are probably at a debug breakpoint. Processes cannot be killed in this state because of the underlying implementation of breakpoints.
The first step would be to go to your Xcode process and stop debugging. If for some strange reason you have lost access to Xcode (perhaps Xcode has lost access to its gdb sub-process), then the solution is to kill the gdb process. More generally, the solution here is to kill the parent process. In your case this is PID 811 (the third column).
There is no need to use -9 in this case.