Or at least Bosses cause on Any % the boss battle is too hard with 100% i like nancys spiked bat that thing takes those guys out with 1 hit

Spiked Bat Nancy hits for 3 dmg

Upgraded Eleven hits for 3 dmg too. You may consider get Eleven's upgrade, maybe will help you. You get this two rooms after getting Mike at School (in a pool at gym).