HITMAN 2

If you can complete it, the Master difficulty "The Classics" challenges will award you enough experience to go from Mastery level 0 to 12, as each of the 3 difficulties has a set of "The Classics" challenges and they stack, whilst also netting you the following:





I used the following video by the fantastic MrFreeze2244:

And here were my end of level challenges/exp screens with this being my first run through of the level:


Following this you will easily be able to clean up the remaining 3 levels whilst completing the 5 Mission Stories on any difficulty of your choice.

To achieve this you can follow the video below to complete the mission as Silent Assassin, Suit Only, Sniper Assassin on Master difficulty which will automatically also get you...


This will already get you a long way towards the mastery level 15 required, and you'll likely be able to achieve the missing levels by replaying the mission on a lower difficulty and following the different (quite entertaining) mission stories.