I found this beetle in my college in Shirpur, Maharastra (central India). What is it? It is very large, and I have never seen it before. I believe it may be Titanus giganteus but I'm not sure.
They are typically large (25–70 mm) and usually brown or black. The males of a few genera sport large mandibles that are used in fights with other males, similar to stag beetles. These beetles are commonly nocturnal and are attracted to light. The majority of the Prioninae whose biology is known are borers whose larvae feed on rotting wood or roots.
For example, your specimen looks a lot like Toxeutes macleayi from Australia.
I'm not sure whether other closely related species live in India (none of the related Indian species that this site mentions look like your specimen), but I would guess if you look into it you might find a local bug guide that might help you find some other related species.
Based on your location in India, I'd say one place you could start looking is through species in the genus Prionus.
they're also large, generally brown or black, are nocturnal. Additionally,
All members of the genus Prionus have twelve or more strongly toothed or even flabellate antennomeres on their large antennae.
- You'll obviously need to provide a better picture for us to examine that detail of your specimen.
I also recommend you examine the list of Indian Prioninae species listed here, including relatives of similarly sized/colored species with large mandibles such as Dorysthenes huegelii and Rhaphipodus fontanieri.
Again, your picture is too low of quality for an accurate ID, but these links should likely help you parse through similar species and hopefully find your answer.