Only uttama-adhikari maha-bhagavata Vaisnava can be diksa-guru

Sri Guru Tattva and the Secret of Diksa
by Srila Bhaktisiddhanta Sarasvati

Rajen Babu: Isn't the kanistha-adhikari qualified to give initiation into the
mantra?

Srila Sarasvati Prabhupada:  Where is the kanishtha-adhikari coming from?
Who gave him the adhikara? A kanishtha-adhikari can never become a guru.

Rajen Babu: Can a madhyama-adhikari give diksa?

Prabhupada: He can only perform the initial duties of diksa. It is the
uttama-adhikari maha-bhagavata Vaisnava who is actually the diksa-guru. 

So many fall downs!Are Iskcon gurus UTTAMA-ADHIKARI?

NoI 5 — “In this verse Srila Rupa Gosvami advises the devotee to be intelligent enough to distinguish between the kanistha-adhikari, madhyama-adhikari and uttama-adhikari. The devotee should also know his own position and should not try to imitate a devotee situated on a higher platform. Srila Bhaktivinoda Thakura has given some practical hints to the effect that an uttama-adhikari Vaisnava can berecognized by his ability to convert many fallen souls to Vaisnavism. ONE SHOULD NOT BECOME A SPIRITUAL MASTER UNLESS HE HAS ATTAINED THE PLATFORM OF UTTAMA-ADHIKARI. A neophyte Vaisnava or a Vaisnava situated on the intermediate platform can also accept disciples, but such disciples must be on the same platform, and it should be understood that they cannot advance very well toward the ultimate goal of life under his insufficient guidance. THEREFORE A DISCIPLE SHOULD BE CAREFULTO ACCEPT AN UTTAMA-ADHIKARI AS A SPIRITUAL MASTER."