Answer

As of now, the largest publicly stated monastic following under one Jain Acharya appears to be under Acharya Shri Mahashraman of the Jain Terapanth. Official Terapanth sources say he is the 11th Acharya and that he has more than 800 monks and nuns under his guidance. ( acharyamahashraman.in)

Explanation

Terapanth follows the principle of “One Guru, One Discipline”, so all monks and nuns in that order remain under the single leadership of the Acharya. The official Terapanth website also states that the order is organized under the complete direction of one Acharya. ( acharyamahashraman.in)

Spiritual Understanding

In Jain Dharma, this kind of disciplined monastic structure helps preserve unity, obedience, simplicity, and spiritual consistency. Under one Acharya, the sangh can move with one direction and one ideal of sādhanā. ( acharyamahashraman.in)

Takeaway

If you mean the current largest Acharya-led Jain monastic group, the answer is Acharya Shri Mahashraman of Terapanth, with 800+ monks and nuns. ( acharyamahashraman.in)