This question resolves to the name of the user with the most-negative profit on the market
Determined based on what I see in the UI when I go to their bets page, e.g. https://manifold.markets/jfjurchen/bets. Note that this is not the same as "actual cash extracted from the market", as it includes what Manifold thinks your current position is worth. If no user has a negative profit it will resolve to the special "No user has a negative profit" response that I will create, because that's cleaner than resolving with PROB of every single Manifold user (they all have M$0 profit). If multiple users are tied for most-negative I will resolve to all of them with equal PROB. If the most-negative user's name is not in the response list then I will resolve to the second-most-negative, etc. If a user's name is in the response list multiple times I will resolve to the one that was added earliest. Adding a duplicate name is throwing your mana away. If you change your username and then bet your new username, I reserve the right to resolve to your original username. Jun 19, 2:06pm: More generally, if the most-negative user changes their username I reserve the right to resolve however I want. Jun 19, 2:13pm: If I am the most-negative user I will not change my username. Jun 19, 2:26pm: Realized the question name is slightly vague. I mean the most-negative profit on this market, https://manifold.markets/jfjurchen/this-question-resolves-to-the-name. Jun 19, 3:03pm: If there is a user with "negative zero" profit (rounded to 0 in the UI, but with a non-zero negative percentage gain like -0.5% so I know they really lost money), then I will resolve to them rather than "no user has a negative profit".
I suspect I'm at a disadvantage here because as the market creator I don't pay fees to myself, so I can't just buy and immediately sell to reduce my profits. But I don't really understand how fees work, or how parimutuel markets work, or how fees in parimutuel markets work.