The following is a list of firepower modifiers that either increase or decrease firepower, causing units and/or structures to deal more or less damage, in some cases even heal.
Note that not all units and defenses are affected by firepower modifiers, which includes unarmed units like MCVs and miners, animals like Attack Dogs, and other units such as the Demo Truck and Charon Tank.
Elite rank -> +40% on promoted unit/upgraded defense that lasts indefinitely
Random crate bonus -> +25% on units/defenses, radius 3
Mercury Strike buff -> +25% on Athena Cannons for 20 seconds, radius 18
Lightning Rod buff -> +25% on Thor Gunships around radius for ~7 seconds, radius 10
Ultra Dome buff -> +50% on defenses around radius for ~8 seconds, radius 9.2
Overcharge buff -> +50% on specific Soviet units/defense for 24 seconds, radius 5
Nuclear Path buff -> +50% on ground vehicles/naval vessels for 180 seconds, radius 1.73
Rage Inductor buff -> +60% on ground/naval units for 60 seconds, radius 4
Dybbuk-Seizer brains -> +60% on ground/naval units for 60 seconds