I should have said, "wins legally by a decision not to prosecute, whether from a grand jury or the state attorney." As you point out, if there is prosecution, there are multiple ways to lose.
There's a current case here that I expect to result in a murder charge. The initial cause may have been some road rage, followed by an in person argument. Shooter got punched, but according to the witness the puncher was walking away when the shooter paused, then drew his gun, and lit the puncher up.
As a friend says: your ego is not your amigo.