A good mango smells fresh, green and clean. It should not have a fermented smell, a sugary scent or any sign of rot. Hold it, inspect it, compare it. Pickling rewards attention. The mango you choose will decide not just the taste of the achar, but its texture, shelf life and final mood.
In the end, the best mango for pickle is the one that looks raw, feels hard, tastes sharply sour and comes home ready for spice. That is where good achar begins: not in the masala jar, but in the basket of mangoes you choose with care.