A K-1 is issued to an owner/investor in the entity.
A 1099-MISC is issued to a subcontractor of the entity.
A 1099-B is appropraite for the trading of securities for your own account.
Some traders are issued a 1099-MISC showing the net income, which might be appropriate if they are truly a subcontractor using the money of the firm and merely getting a percentage of the gains paid to him for his services.
When there are no net gains, rather there are net losses, this method falls somewhat short and it is up to the individual to properly maintain his sole proprietorship records along with his letter of agreement, to reflect his reportable tax numbers.