What IceBear said.
The main reason that the -4 even deserves mention is because one will occassionally get positive modifiers to damage. Say the creature at issue has bull's strength cast upon it and gains +4 Strength, for a +2 damage bonus. Its damage will now be 1d2-2 (still a minimum of 1). If, OTOH, it gets a super-strong double-Empowered bull's strength, for a +10 Strength bonus, then its damage would rise to 1d2+1, which is a 2-3 hp damage range.