If the defendant kills themselves before trial, that's a failure to prosecute. If the prosecutor caused that suicide, that must count against them, no?
Why would it count against you if you are performing your duties both morally and legally, and something outside of your control and responsibility happens? So, no. This does not count against.
I have difficulty seeing driving a (apparently innocent) defendant to suicide as morally defensible. Besides, their goal should be conviction, not death. They failed to secure a conviction. They failed.