In a competition or game:
* Lost - The most direct opposite, meaning to not win.
* Tied - A situation where no one wins.
In a general sense:
* Lost - Can also be used to mean to not succeed in general.
* Failed - A more formal way of saying you didn't achieve something.
* Missed - Can be used for opportunities or targets.
To be more precise, it would be helpful to know the full sentence or situation where "won" is used.