By "harming a market", I mean "causing a market to be less efficient". It is typically easier to identify harmful behavior than it is to quantify the amount of

By "harming a market", I mean "causing a market to be less efficient". It is typically easier to identify harmful behavior than it is to quantify the amount of harm caused. Sometimes you can easily estimate a rough lower bound on the harm's cost. Easier cases include 1) Spoofing, where you could estimate the harm as being greater than the captured profit, and 2) Self-trading for the purpose of receiving liquidity provider incentives, where you could estimate the harm as being greater than the incentives received. Harder cases include situations where poor strategies caused market instability by underestimating risk or trading in a way that is too similar to others. Extreme examples of these include the Long-Term Capital Management (LTCM) blowout in 1998, the 2010 Flash Crash, or any number of firms that contributed to the financial crisis of 2007-2008. You should be able to find plenty of academic papers attempting to quantify the harm of those.