Here you will find the list of every weapon that you can use in Cuphead with the detail of their damage which you can do to bosses and other enemies.
|Peashooter EX||8.33 per hit, max 25|
|Spread||6.2 (when all pieces hit)||41.33|
|Spread EX||5 per shot|
|Charge (max)||52||40.00 with perfect charges, 37.5 for me|
|Roundabout||8.5 (the direction you shoot is irrelevant)||31.875|
|Roundabout EX||5 per hit, max 35|
|Super 3||4 per hit, max 112|
|Plane bullet EX||15 per hit|
|Plane bomb||11.5 for direct hit, then another 11.5 for the explosion||37.30|
|Plane bomb EX||6 per hit, max 54|
|Mini plane bullet||2||20.00|
|Plane super bomb||152|
The extra heart charm gives -5% damage. The double heart charm gives -10% damage.
The info in this guide was provided through testings made by reddit user Hypen-ated using Cheat Engine tool to merely monitor the bosses HP while damaging them.