The Last Battle
I think David Eddings wrote this first, or shortly after the prologue, and then built the story from here. What happens when two forces who are destined to meet, with the stakes of the world (well, galaxy—but I’ll get to that later) at hand, transform into the literal representatives of the force of good vs. the force of evil? I think this is the best-written part of the series, and coming from Wheel of Time I think it’s worth the read. In fact, it seems Robert Jordan (at least in his notes, and whatever he left for his estate) pulled from this almost word for word for Wheel of Time.
This is also where Robert Jordan gets his theme of personal choice. The last battle in The Belgariad was predetermined to go one of two ways. There weren’t other options—both champions couldn’t survive. To a point, an argument could be made that before the battle there was a choice someone did make, but that choice either way supported one of the two sets of detailed prophecies. There wasn’t a third way that choice could go.
A few more points to contrast this story with Wheel of Time: The two champions grow and battle each other above the city they are in. This, at least to me, relates to the closing of the second Wheel of Time book where they are seen as giants in the sky. Also, in The Belgariad the main character is frozen as some events are happening right before the last battle. I think this was some inspiration for Robert Jordan when he has Rand and Moridin locked together, seemingly frozen in place.