Fighting and Hexproof

[Nefarias]

My opponent controls a Rotting Fensnake and a Dross Crocodile. I cast Blood Feud targeting the two of them. My opponent responds by casting Ranger's Guile on the Fensnake. What happens?

Blood Feud: [Sorcery] Target creature fights another target creature.

Ranger's Guile: [Instant] Target creature you control gets +1/+1 and gains hexproof until end of turn.

[Clariax]

One of the targets is legal and one is not legal, so the spell will resolve and do as much as it can, but not be able to do anything to the illegal target.  End result is the spell doesn't do anything.  It cannot make the illegal target do any damage, and it cannot make anything do damage to the illegal target.