Sage mode. Although Sharingan could block almost every attack. If the user gets hit with one he or she will be seriously or fatally injured.
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I guess you are refering to Sage mode. Sage or Hermit mode is when someone trained in senjutsu has made Sage chakra (normal chakra mixed with energy from the nature). In sage mode, ninjutsu, genjutsu and taijutsu are stronger, the user becomes stronger and a lot of things. Follow the link for more info.
Sage mode increases speed and strength and Sauske's mangekyou sharingan is used for ninjutsu and genjutsu. So I would go with Naruto.
If you really meditate hard, and put your spiritual power and blend them with nature you would be able to achieve sage mode, just make sure u put some makeup when you have accomplished sage mode, you want people to know your on sage mode for safety purposes.
If you think how strong chakra is without natural energy, it should make Naruto at least 1/3 stronger considering there's 3 types of chakra now.
sage mode