Psycho
"Psycho" is a series of challenges available in Dying Light. They're given by Jeffrey in the Safe Zone due north of the tower.
During the first challenge, the player is tasked with cutting off 30 zombie arms within the time limit. While the player starts on the top of a building with enough zombies to complete the quest, it may become difficult to complete since kills that don't sever arms don't count. It is possible to leap off the building in a few places, such as the corner behind and to the right of where the player spawns, and land safely on top of cars, which allows the player to finish an otherwise uncompletable challenge.
During the second challenge, the player is tasked with killing 15 zombies by throwing them into spikes. While the challenge specifies using grapple, any attack that drives them into the spikes counts.
During the third challenge, the player is tasked with breaking the legs of 25 zombies using a baseball bat. It is unconfirmed whether breaking 2 legs on one zombie counts as 2, but easy to accomplish as the zombies are in hordes. A good strategy is to slide under the zombies and kick, as that almost always breaks their legs.
During the fourth challenge, the player is tasked with cutting the heads off 30 zombies with a sword. This is in a bus station and there is a spitter on the roof of your starting location but there are plenty zombies around to avoid the spitter hitting you.
During the fifth and final challenge, the playing is tasked with cutting 30 zombies in half with an axe. Probably best for your auto aim to be off with this one as it's very challenging because the axe doesn't swing so fast. A tip would be to use firecrakers to lure a hord of zombies together so your axe cuts many in half in the same swing.
When all tasks are complete there is one final battle to come and that's with Jeffrey in the safe zone.