The destructive power of the Rinnegan was not all that impressive to him. Even an Almighty Push unleashed at full power had only destroyed one Konoha Village. His Kamehameha, fired at full strength, could wipe out most of an entire city.
That was without loading the Goku Template to stack Combat Power or using Great Ape Transformation.
What he truly valued was the Rinnegan's power to resurrect the dead: Rinne Rebirth. It was an incredible ninjutsu that could revive every Hidden Leaf Ninja who had died in an entire village—even if their bodies had been obliterated.
Bringing the dead back to life was a peak-tier ability in any world.
Of course, the cost was enormous. Nagato had paid with his own life, and there were limitations: the targets had to have died only recently.
But that did not matter. His physique was nothing Nagato could compare to, and he would not revive so many people at once. Anyone worth using this ability on would surely be extremely important to him.
Secondly, he also valued the Rinnegan Human Path's ability to extract souls and read the memories within them.
With his current soul power, when he loaded the Harry Potter template, he could easily use Shinigami Power to erase Voldemort's soul.
However, he could not read the memories contained within that fragment of Voldemort's soul.
But once he had the Rinnegan Human Path's ability, he could examine all of Voldemort's memories from beginning to end and learn every spell Voldemort had mastered in his lifetime.
There was Fiendfyre Curse, whose power was no weaker than Amaterasu; Apparition, which allowed instant movement; Memory Charm, which could alter and erase memories; Legilimency, which could read minds; and more.
If he was lucky, Voldemort might have researched Time Magic such as the Time-Turner Spell.