If I have a creature that has 0 or negative power and it has a Viridian Longbow attached to it, does it still deal 1 damage because of the effect the equipment gives it, or does it not because of the negative or 0 power?
Magic: the Gathering cards usually mean exactly what they say, nothing more and nothing less.
The power of a creature is only relevant when
- Dealing combat damage
- An effect explicitly mentions the power of that creature (albeit maybe hidden behind keywords, like "fight")
The ability granted by Viridian Longbow doesn't mention the power of the equipped creature, so therefore it doesn't care. One damage is dealt regardless.