In order to get Lu Bu's level 11 weapon you must get 2,000 KOs. Its useful to have a second player to help get the weapon. Kill enemy officers that stand in your way, including sub officers if desired. Ave the other player be a decoy for enemy officers. It is best when Liu Bei and his brothers kill Guan Yu and Zhang Fei first, leaving Liu Bei alive. While standing by a gate captain, you can get an incredible amount of kills when major pains are gone.