What is Koffing becoming and how does it transform? 

koffing evolution becomes Weezing at level 35. As it evolves, it acquires better stats particularly in defense and special attack. Weezing is also able to make more powerful moves and resist attacks. Some, such as Galar, are typed by Fairy. Koffing will become more competitive and helpful in the battle with the help of evolution, and it is more helpful to those players who use more defensive approaches.