Upvote:6
There is no specific, global threshold for what level of damage would render a passport damaged sufficiently to the point where it could not be used. It will at the discretion of the immigration officials, and potentially even the airline staff, to make this determination.
The concern for damage on the "bio" page as this is will not so much be the damage itself (which appears relatively minor), but instead the possibility that this damage occurred during an attempt to modify the passport - such as changing the photo to resemble someone other than the legitimate passport holder.
Additional, if the damage has resulted in the loss of any of the security features of the passport, such as any holograms that exist on the bio page covering, then this could also be seen as an attempt to modify the passport.
It's not possible to tell from the photo you've included whether this damage could be indicative of an attempt to modify the passport or not, although it does not appear that it would.
If your passport is an "e-Passport" then you have the additional benefit that there is a 2nd copy of the photo in your passport - on the "chip" contained within the passport. Immigration staff will be able to access this copy of the photo and confirm that the photo on the passport has not been (significantly/deliberately) modified, and does match you. Unfortunately India has been slow to issue such passports, and it's unlikely that you have one.