In my opinion, Bangers is the best clan for KO in two turns. First thing you have to do is calculating the maximum attack of your opponent (e.g. 7 power * 13 Pillz = 91 attack). Then, you need to find out how many Pillz you need in order to pass that maximum attack. So, let's say you need 8 pillz; if you need 8 Pillz, you can freely put 6 Pillz on the first round. I don't say that this tactic works ALL the time; however, I can easily say that it works with 60 - 70% of success and I think it is enough for me. However, this tactic will have a greater chance of failure if it is used against the following clans: Nightmare, Piranas, Ulu Watu, Bangers and All Stars.
First of all, Nightmare and Piranas cancel your +2 Power clan bonus. In addition, fighting against Ulu Watu or Bangers destroy the significance of your own +2 Power clan bonus, since they have the same bonus. Finally, the characters of All Stars have a clan bonus of -2 Opp. Power, which simply means canceling your clan bonus. However, if you have Ambre, things will be much easier for you.
Let me tell you my deck: Ambre, Willy, Vermyn N, Shann, Fixit, Bodenpower, Blaaster Cr, Angie. Only Blaaster Cr costs too much when compared to other characters, but every rose has prickles, right? Thank you for bothering reading.