Moshiach's level is so great, it brings tzaddikim to tshuva

לאתבא צדיקייא בתיובתא—ראה זח"ג קנג

"Tzaddikim will be brought to tshuva"—this is specifically referring to Moshiach, as explained that Moshiach is the one who will bring tzaddikim to do tshuva because the level of the neshoma of Moshiach is incomparable to the level of the rest of the neshomas. This is known from the writings of the Arizal—that the level of neshoma that the greatest of Yisroel received prior to Moshiach are only from the aspects of נרנ"ח (nefesh, ruach, neshoma, chaya). Adam Harishon merited to chaya, which is not the case with Moshiach who will merit to Yechida [essence of the neshoma, one with Hashem], the Yechida klolis (the collective Yechida) of all of Yisroel. And the aspect of Yechida is incomparably greater compared with נרנ"ח (nefesh, ruach, neshoma, chaya).

Lubavitcher Rebbe, Sefer Maamorim Meluket I, p.160 (Free Translation)