There are 5 harlequins to beat up with your fists.
If you kill one by accident or if you go to the location and they aren't there then just run around and keep checking. They will eventually appear/respawn and the game will notify you how many you have beaten up after you do it correctly "X of 5 Harlequins beaten up
These are the 5 locations that they are located:Tip 1:
You know if you are in the right area if you see a guy or two sitting down drinking, I found that usually if you bump into them, and they get up and walk away, it spawns the harlequin after a few seconds..........Tip 2:
The easiest and safest way to take them out is to use a smoke bomb, switch to your fists, and its a one hit KO!!!!!
Special thanks to Warboy925
for the tips