The way you formulated a question is not conducive to getting the answers you want, because people start thinking of something along the lines of the Holocaust, 9/11, or other memes associated with evil.
I recommend rephrasing it as follows: point out the most anti-altruistic legal ways a person or an organization have spent $1M. Thinking about it this way, there is no shortage of examples, none resulting in Kawoomba losing much sleep. In fact, a large chunk of what most governments do is both legal and anti-altruistic.
For example, suppressing one's right to die with dignity, and thus forcing doctors and nurses to torture thousands of helpless and elderly people against their will, often for years, before they are allowed to finally die, is arguably legal, anti-altruistic and doesn't cost a lot to perpetuate. The resulting disutility by most measures outweighs 9/11 by many orders of magnitude.
Another example: resisting self-driving car adoption. This one is even worse, given that every year self-driving cars are delayed, costs about 30,000 lives in the US only.
Just look around you, money is spent in anti-altruistic ways all the time.
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.