Firstly, Naruto said it after using the rasenshuriken against the third raikage whose defense is amazing and very powerful.
Secondly, Gaara's defense broke kimimaro's strongest bone (when he was in curse seal level 2) which oro said was impermeable to any physical attack.
Thirdly, Gaara was able to block a C3, something that could destroy a village.
Fourthly, even his sand amour was able to withstand rock lee's 5 gates attack.
Lastly, he was able to block raikage's( when wearing the strongest form of his lightning amour) kick and blocked amaterasu also.
Your opinions please, no insults.
Secondly, Gaara's defense broke kimimaro's strongest bone (when he was in curse seal level 2) which oro said was impermeable to any physical attack.
Thirdly, Gaara was able to block a C3, something that could destroy a village.
Fourthly, even his sand amour was able to withstand rock lee's 5 gates attack.
Lastly, he was able to block raikage's( when wearing the strongest form of his lightning amour) kick and blocked amaterasu also.
Your opinions please, no insults.