After Sun Mo looked at Fang Wuan's data, he surmised that this fellow had an 80-90% chance of fighting all the way to the death.
Although his Immemorial Vairocana was a saint-tier cultivation art, its main purpose was to hit out the cultivation arts of others. In terms of attacking prowess, it was one level lower compared to other saint-tier cultivation arts.
Hence, Sun Mo had used himself as the bait, depending on his Invulnerable Golden Body to block his opponent's ultimate move. After that, he used 'Paying someone back in their own coin' to retaliate.
The Invulnerable Golden Body diminished a portion of Fang Wuan's sword might. Hence, Sun Mo's inner organs were fine, and he had only suffered a huge wound on his chest. However, Fang Wuan was in a much dire state, his inner organs were destroyed by Sun Mo's blade.
One died, while the other was heavily injured. No matter how Sun Mo looked at it, he had profited.