Final answer:
Dhruva, Prahlada, and Radha are examples of devotees who achieved perfection by practicing one process of nava-vidhä-bhakti.
Step-by-step explanation:
In Bhakti tradition, there are nine forms of devotional service called nava-vidhä-bhakti. Each form focuses on a specific method of achieving spiritual perfection. One example of a devotee who achieved perfection by practicing simply one process of nava-vidhä-bhakti is Dhruva. He achieved perfection by engaging in constant meditation on Lord Vishnu.
Another example is Prahlada, who achieved perfection by constantly chanting the holy name of Lord Vishnu.
Radha, the eternal consort of Lord Krishna, is also considered a perfect devotee who achieved perfection through pure love and devotion to Krishna.