To start 'Villans of Valencia' you will need to be negative karma. I recommend negative 70-80k.

The fastest way to achieve this is kill a friend a couple of times. (There are other ways to get negative karma but it takes FOREVER)

Extra tips:
To get knowledge of Kayal Nesser. You will have to complete a questline from Bertod. You will have to kill 200 mobs in Pila Ku Jail and then a second quest where you have to run around and find a certain item from marked spots (RNG)

You can NOT equip boss gear from Jetina when negative karma. So make sure you have some spare gear or ask a friend to help you kill the mobs whilst you run around.

Once done with getting all the knowledge of the people. You can head back to Pila Ku Jail and kill mobs until you are positive karma again.