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Anubis, Osiris, those are the two I mainly assosiate with the afterlife. They both witness the weighing of the heart (done by using Ma'at's feather of truth), which is recorded by Thoth. You also have the God who devower's the dead's heart, but I have forgotten his name (oops). Horus guides the dead to be judged by Osiris.

There are alot of Gods involved.

Yea, I'm fairly certain it's Osiris.

Anubis was the god/guardian of embalming, tombs & watching over the dead themselves but the 'evil serpent' of the Underworld I think was Apep.
In egyptian he was known as Apep but the Greek found out about him and named him Apophis.

There is no 'real' god *of* anything in Egyptian mythology. Nearly every god is associated with and/or identified as nearly every other god.
There is no simple one to one correspondence of 'god' to 'thing whhich this god represents' as the more simplified introductory texts would have you believe.

Egyptian religion is the result of thousands of years of change and evolution, of local gods, pantheons, beliefs and practices being incorporated into a large and somewhat patchwork system of beliefs which differs according to place and time.

Some sort of jackal god was known in pre-dynastic and early dynastic times, this god may have been the same as (or an early form of) the early dynastic jackal Khentyimentiu (Foremost of the Westerners) who does have some sort of connections to the necropolis (but also to various sacred locations.
This god may have developed into or given rise to the jackal god Anubis, who may have been the original deity associated with the dead,
over time the god Osiris (who may have been initially a local deity) gained prominence as the main god associated to the underworld/afterlife (and also, being a god of the 'dying-rising' type, with fertility, rebirth and the cycles of agriculture) and Anubis became primarily associated with embalming and a sort of god of the transition into the afterlife.
Mythology and the set up of hte pantheon does not necessarily parallel the actual historical developments (where we even *can* trace these).

These are really two different versions of the sun journey.

I have to go with many here and say They can't be put into boxes like that. However, if I had to pick one I'd go with Osiris.

Wesir/Osiris is the King of the Underworld. Yinepu/Wepwawet aka Anubis is more like the guide of the Underworld, leading those blessed souls past the bad things into the weighing of the heart. The thing is, unlike the Christain Underworld, the Kemetic/Egyptian Underworld isn't "Hell"... it's more like limbo.