Raise a weapon type to the maximum levels, then defeat 500 enemies to unlock the 
level 4 weapon type for that character. Note: Each type of weapon is only 
unlocked based on your own weapon. Hence, a sword unlocks level 4 swords, etc. 
Alternately, play Empire mode on any difficulty setting. Defeat the main Boss of 
a stage in less than four minutes to get a level 4 weapon at the end of the 
stage.
Play the level where you rescue the Emperor from Li Jue, Lubu, etc. Go to where 
Li Jue is located and kill him. Near him should be a gate where men constantly 
pour out. Have your men fight the Gate Captain while you stand directly in front 
of the gate (where you cannot walk towards it any more). Do not kill the Gate 
Guard as this will stop the reinforcements. Just remain there and attack, 
killing all the men you come in intact with. Once you get 1,000 K.O.s, complete 
the level.