From the Menu--Professional--Weapons--Batter Up (15 minutes) --Medium--
Grab the bat upstairs in the safehouse in front of you. Melee weapons break so use the execution (press ) option when it pops up (usually after two swings) to save its 'ammo'. Head north to Tattaglias 'Global Trading Co' and kill the 3 Tattaglias outside, ignore the 2 Tattaglias in the back alley because your bat will break before you are able to get a new melee weapon. Extort the owner to unlock the back door and kill the 1 Tattaglia. The next room holds 3 Tattaglias and there is a civilian holding a lead pipe that you can kill (without penalty). Use a gun because he'll fight back and you'll need this when your bat breaks. Upstairs there are 3 Tattaglias and a tire iron that you can pick up (press ). Do Not extort the Racketeer. There is 1 Tattaglia on the roof, use the elevator lift to reach him. Face a wall and throw a moltov to kill yourself. Repeat 2 more times, and you should get 11 kills each time.