I'm not sure. I would have to be in the situation to decide, and I would probably carry that decision around for a long time, wondering, given the following.
On one hand, I could see myself doing it. If I decided to marry and raise children, $1,000,000 would be an invaluable financial relief: college(s), potential medical issues, sufficient dwelling space, exposure to various interests (music, art, dance, martial arts, whatever), and so on. Additionally, spending the money in self-interest could mean financing school programs and such because education is very important to you. If I had the power to send students to say, Ravenna to see all of the art there first-hand and better understand the time period leading up to the Dark Ages and thus, have a more complete understanding of history, I would do it. Less drastic: something like funding textbooks and repairs/upgrades could make a difference. The list goes on.
If I were to kill something that had never wronged me, it would be clean and painless. As the OP did not put any parameters, I'd put it to sleep first, then inject something else to stop its heart so it wouldn't suffer. I would probably then cremate it and keep its ashes as a reminder of the cost. Torture is against my rule-book.
On the other hand, I'm not sure I could make myself do it. Thinking about the act gives me a headache and my body tenses up and shudders a little. Famed historic wars and slaughters come to mind - the Crusades, the American Civil War, the French Revolution, and the World Wars, in particular - and I wonder: where does it end? Is it us that permits, and to an extent, encourages this behavior, or is it our placement? I think it lies somewhere in the middle, around Zen Buddhism and looking outside one's self. But I digress, and need to take a peaceful walk for the headache to go away.
