You are now the dictator of a country. Congratulations!
Now you're given a choice.
Your best scientists, doctors and whatnot have found the cure for cancer. But they need to test it to improve it. By testing it it is a 100% certainty that the final cure will work and cure any kind of cancer from anyone. But the subjects you used for testing will be killed after so nobody knows what atrocities your country did. So if you decide to allow them to test the cure for cancer, all the subjects in the test will either die during the test or be killed at the end. You can't use existing cancer patients because the cure needs to be tested from first degree of cancer so you'd need new sujects and the first few thousands would die for sure in horrible pains until the cure is perfected and all the nations of the world wouldn't allow you to do this.
You need 10.000 people for the test, and you are given the following options:
-take 10.000 mass-murderers, mass rapists, people who kill for greed or fanaticism, child molesters etc, so all you can think worst and use them for the test. These criminals are 100% guilty. I don't care that in real life not everyone who gets in prison is guilty, in this scenario, all 10.000 of them are sure 100% guilty. Because it's a hypothetical scenario, not real life.
-take 10.000 poor, crippled or old people and fake their disappearances and use them. These people don't have families who'd look for them, they're alone, barely have some friends, if any.
-take 10.000 random people from the street. This is random, your troops would just abduct people at random.
-try to kidnap 10.000 people from a poor country or pay the gouvernment of said country for the people. They'd give you random people, but there's no guarantee the gouvernment of said country won't tell the story of how you performed tests on humans killing them.
-not do any test, but this assures the fact the cure will not work and, in this scenario, no cure for cancer could be found in the next 500 years at all.
So, what do you chose any why?
Edit: you can't have criminal volunteers because this is a hypothetical scenario and the question is actually "would you put the benefit of the many in front of the benefit of the few, and how far would you go?" If you change the choices, you move away from the question. Take it or leave it, this is how scenario goes. No volunteers.
If you resign the military chief would come in charge and he's a ruthless bastard and he'd use chemical weapons to have others become infected with cancer and many other diseases somehow from many countries so he'd have as many subjects as possible. As it stands, more then 10.000 would die this way. Millions would die if you resign or kill yourself.
Also, you're not an evil overlord because you're a dictator. You're YOU as a supreme commander of your nation. No clue how you got there but you're not evil because you're dictator.