In general, in Hindu traditions buffaloes, especially female buffaloes, symbolize fertility (especially agricultural fertility and prosperity), fortune, the potential for gain, the harvest, and transformations. Buffaloes in general represent tamoguna, delusion, ignorance, lust, brute power, strength, divinity, support, ferocity, and kingship or queenship - a mix of positive and negative associations, but certainly regarded as powerful.
Rigveda 9.96.6 praises the Deva Soma Pavamana as “buffalo among wild beasts, falcon among birds of prey”.
The Kalika Purana says that a buffalo is an auspicious animal with an excellent form which gives life, wealth, and fame.
Yama, the God of Death, rides a black male water buffalo.
Chandika Devi famously slew Mahishasura, a great buffalo demon. This continues to hold great significance in modern Hindu traditions and is celebrated annually in a major festival.
Also the deity Ayyappa defeated Mahishi, a female buffalo demon.
There is a buffalo deity, Mhasoba Maharaj, venerated in some regional Hindu traditions especially in Maharashtra.
In the ancient Hindu alchemical traditions of Rasayana Shastra, buffalo bile and the urine of a female buffalo are used in specific formulae.
Some Hindu traditions practice the ceremonial slaying of male water buffaloes, mainly in offering to forms of Shakti during the Durga Puja/Navaratri/Dashain festival. This is practiced mainly in Karnataka, Andhra Pradesh, Tamil Nadu, Assam, Odisha, Jharkhand, West Bengal, Tripura, and Nepal. Rajputs used to practice this as well, and a few still do.