I'm probably going to end up on a list for saying this might be possible.
Most evil thing I can think of?
I've not put much time into it but I'll take a swing at it. My top candidate would probably be to use the million to set up DNA synthesis company making custom DNA sequences to sell to university labs and similar.
The company probably wouldn't survive very long term as there's established companies already in the field but there's a good chance that it would allow you to leverage that million bucks to get more investment and most importantly leave you in a position where, once you have the equipment, you can synthesis your own sequences un-monitored. (hence why you wouldn't just use the million to pay an existing company to do it)
It'd be a huge task but then you could synthesis the 180K bases of smallpox, building it up from small synthesized sections, culture it and release it into the human population through contaminated letters sent to many many unimportant people in every country in the world at once.
Make sure to leave a manifesto where you claim to have done it "for science" to smite the "unscientific" and commit suicide in a manner which leaves no body or proof that you're dead so that there will be an eternal hunt for you and eternal fear of future attacks.
Hundreds of millions dead, one of the greatest achievements in human history reversed, economic turmoil across the globe, biotech and bio research probably permanently crippled, science itself demonized, blamed and hated.
Definitely illegal, by virtue of being bioterrorism, also I believe that you underestimate the difficulty of synthesis and overestimate how fast your epidemic could spread before being re-contained.
Edit: The purpose of this question is not to make the world worse, but to see whether we actually have concrete ideas of what would, and my guess is that most of us don't, not in a really concrete way. From the downvotes I'm wondering if everyone else is thinking way darker directions than I am. If so please share.
There is a lot of discussion here about effective altruism. Organizations like GiveWell with donations, using criterion like quality-life-years-saved-per-dollar. People distinguish warm-and-fuzzy giving from the most effective use of dollars from various utilitarian perspectives.
But I want to ask a different question: What would effective anti-altruism be?
To make it more concrete:
I am an eccentric multimillionaire, proposing a contest to all of you, who will for the purposes of this exercise play greedy and callous, yet honest and efficient, contest entrants.
Whoever can propose the most negative possible use for my money, in the sense that it causes the greatest amount of global misery, (feel free to argue for your own interpretation of the details of what this means) will receive $1 million to carry out his or her proposal and $1 million to keep for him or herself to with as desired.
A few rules:
1) Everything must be 100% legal in whatever jurisdiction you propose. Edit: People had trouble with the old phrasing, so I'll add that it should not only be legal in the letter of the law, but also in some reasonable interpretation of the spirit of the law.
1a) In fact, I encourage you to think of things that aren't merely legal but that would also be legal under whatever your favorite hypothetical laws are. Maybe that means non-coercive, non-violent, or something else in that vein.
2) This money may be used as seed funding for a non-profit or for-profit anti-altruistic venture, but I will take into account both the risk and the marginal impact of only the first million dollars.
3) Risk and plausibility are factors just as they would be in any investment for effective altruism
4) If you're going to propose that you keep and embezzle the first million dollars, you should have an extremely good justification for why such a mundane plan would match my standards for anti-altruism.
I hope this pushes you all to think of truly anti-altruistic means of spending this money. I think you may find that effective anti-altruism is a good deal harder than you'd believe.