To kill Cardoso, Guding only used the Mirror Dao. His power of Dao was stronger than the opponent, hence the crushing defeat.
Originally, if it were a face-to-face confrontation, Cardoso wouldn't have been taken down so easily. But he had been besieged by Berg and the others, exhausting a lot of his power of Dao. Additionally, his final burst move almost drained more than half of the power of Dao in his body.
Guding's Mirror Dao not only could reflect the opponent's attacks but also enhance them according to the strength of his internal power of Dao. The final attack that was reflected back was more than twice Cardoso's original attack. Engulfed by the Sword Sea, Cardoso lasted less than three seconds and was completely crushed into smithereens by his own enhanced Divine Skills.
