Maha Mantra– mantra for kali yuga.

“In this Age of Kali, people who are endowed with sufficient intelligence will worship the Lord, who is accompanied by His associates, by performance of saṅkīrtana-yajña.” Other yajñas prescribed in the Vedic literatures are not easy to perform in this Age of Kali, but the saṅkīrtana-yajña is easy and sublime for all purposes, as recommended in Bhagavad-gītā also (9.14).
Source : https://vedabase.io/en/library/bg/3/10/