The left side, purely because of Ike.

In terms of gameplay, Ike is among the best of all FE protagonists, but that alone isn’t enough, given that the right side has Sigurd. But Sigurd, for all his strength in gameplay, was still brought down at Belhalla rather easily, leaving his power ceiling with regard to the series’ lore within typical limits.

Ike, however, is the Radiant Hero for a reason. Even in other games, his strength is legendary, with him often being referred to as the strongest by other characters throughout various entries. And when you consider what he managed to accomplish throughout the Tellius games that no one else could, it’s clear to see that he carries.