Superguard

The Superguard is a more advanced version of a guard used in Paper Mario: The Thousand-Year Door. It stops any attack (with the exceptions of a few bosses and mini bosses) from doing any damage at all, blocks any status effect, including Immobilize, and any direct-contact moves will be returned to the attacker, costing the enemy one HP of damage. This counterattack damage does not stack with other counterattack effects such as being electrified. On indirect-attacks, the Superguard will simply negate all damage, with the exception of a Pokey's body segment throw attack, which will send the body segment back to the Pokey and cause the same amount of damage the attack would've done to Mario or his partner. The counter-attack effect of the Superguard does not work on the Armored Harriers. Neither Mario, his partner nor the Iron Cleft that hit them will take any damage, presumably to force the player to acquire Yoshi to defeat them.

Timing
Despite being incredibly useful, it is even harder to execute than a guard, requiring a press of 3/60th of a second (3 frames) before contact compared to a guard's requiring a press of  8/60th of a second (8 frames) before contact. Two Simplifier badges or one Unsimplifier badge will respectively loosen or tighten the window to guard by 1/60 of a second. If done correctly, Mario or his partner will spin around and words will pop out next to them saying "GREAT" in orange; compared to just guarding, Mario or his partner will just retain a ducked position, and the words say "NICE" in blue.

Unguardable attacks
Aside from items used against Mario and his allies, the following attacks in the game are those against which the player cannot guard or Superguard. Additionally, in the Japanese version of the game, none of the Shadow Queen's or Smorg's attacks can be Superguarded.
 * Hooktail, Gloomtail and Bonetail’s Bite attacks
 * Bulky Bob-omb's & Bob-ulk's Explosion
 * The Shadow Queen's Shade Hands attack (the player can guard however, making it the only attack that can be guarded but not Superguarded)
 * Vivian's Fiery Jinx
 * Marilyn's Thunder

Trivia

 * The Pixl Barry's ability in Super Paper Mario is very similar to the Superguard; their animations are very similar (spinning in place), and both require good timing (though Barry's doesn't have to be very precise) in order to deal damage to the opponent and protect the player from damage.