Considering how much was on stake I think somebody could have sacrificed themselves to kill Hitler.
In the end they all ended up dead.
We usually associate suicide attacks with acts of terrorism, but in some ways they may be ethical, even heroic. After all, instead of having a bigger bomb, to assure destruction of the evil dictator, you can approach the evil dictator closer as you detonate yourself. These would ensure less collateral damage, like to the soldiers guarding outside, or civilian servants.
Of course, to kill yourself, besides being very dedicated to a cause, you need to have a religion that allows it, or preferably rewards it (e.g. Islam)
Alas, German Catholicism or Protestantism, Von Stauffenberg believed in, didn't cut it !