In fact, the fastest way to level up any perk is to simply focus on using perk weapons to kill Zeds. weld the door, unweld the door, weld the door, unweld the door) and the scarcity of enemies we needed to kill a certain number of (e.g. This is a huge relief for those of us unimpressed with the necessity of doing stupid things (e.g. healing), but it is not a requirement in order to level up. In KF2, this process has been streamlined so that you receive XP from doing class-related things (e.g. These were mostly an annoyance, silliness done in between waves when you were just waiting for the seconds to tick down and the next wave to start. door-welding, amount of healing done, etc.). To level up your perk in a particular class in KF, you had to use one of the class's corresponding weapons to do a certain amount of cumulative damage against enemy Zeds - and there would also be an additional requirement per class that you would also need to farm (e.g. (see Class Guide: How to Play Berserker, Commando, Medic, Support for a look at the different perk rewards) Each time you gain a level, your stats are increased by a small percentage, and after each 5-level increment, you choose between two different level perks. Each class currently has 25 levels while in Early Access.