Emperor.

While it was true that the Gold Vein Spirit Seeking Lilies could increase one's soul by 1% of strength indefinitely, this was a bit misleading. It could be said that the limiter was one's soul itself as opposed to the Spirit Seeking Lilies. 

Even if one had an infinite number of Gold Vein Petals, the largest they should be capable of making their soul was 9.9 centimeters tall. Hitting 10 centimeters should be impossible. 

To put matters into proper perspective, even being born with a Soul Nature didn't guarantee having an Indestructible Soul. Only a small percentage of these individuals would ever reach such a level. This was all to say that unless you were innately born with an Indestructible Soul, even becoming a Sky God wouldn't change this fact!