Lord Viṣṇu is the mahā-puruṣa. Therefore one who becomes a Vaiṣṇava attains the position of a mahā-pauruṣya. This position was attained by Mahārāja Parīkṣit. It is said in the Padma Purāṇa that the distinction between a demigod and a demon is that a demigod is a devotee of Lord Viṣṇu whereas a demon is just the opposite: viṣṇu-bhaktaḥ smṛto daiva āsuras tad-viparyayaḥ. Vṛtrāsura was considered a demon, but actually he was more than qualified as a devotee, or mahā-pauruṣya. If one somehow becomes a devotee of the Supreme Lord, whatever his position, he can be brought to the position of a perfect person. This is possible if an unalloyed devotee tries to serve the Lord by delivering him in this way. Therefore Śukadeva Gosvāmī says in Śrīmad-Bhāgavatam (2.4.18):

kirāta-hūṇāndhra-pulinda-pulkaśā
 ābhīra-śumbhā yavanāḥ khasādayaḥ
ye ’nye ca pāpā yad-apāśrayāśrayāḥ
 śudhyanti tasmai prabhaviṣṇave namaḥ

“Kirātas, Hūṇas, Āndhras, Pulindas, Pulkaśas, Ābhīras, Śumbhas, Yavanas and members of the Khasa races, and even others addicted to sinful acts can be purified by taking shelter of the devotees of the Lord, for He is the supreme power. I beg to offer my respectful obeisances unto Him.” Anyone can be purified if he takes shelter of a pure devotee and molds his character according to the pure devotee’s direction. Then, even if one is a Kirāta, Āndhra, Pulinda or whatever, he can be purified and elevated to the position of a mahā-pauruṣya.