Kishi stated in Databook 1 that Prime Hiruzen is the strongest of all time.
Kishi had numerous chances to retcon this. He didn't. Even in Databook 4, he made no indication that someone was stronger than Prime Hiruzen.
There is no evidence to show that Prime Hiruzen isn't the strongest.
But there is evidence to show that Prime Hiruzen is the strongest: the databook
Kishi had numerous chances to retcon this. He didn't. Even in Databook 4, he made no indication that someone was stronger than Prime Hiruzen.
There is no evidence to show that Prime Hiruzen isn't the strongest.
But there is evidence to show that Prime Hiruzen is the strongest: the databook