Passive euthanasia(means of the withdrawal of life support to patients in a permanent vegetative state) is legal in India.So I think you are talking about Active euthanasia(Active euthanasia entails the use of lethal substances or forces, such as administering a lethal injection, to kill and is the most controversial means).

No Active euthanasia should not be legalized in India, how could we legalize something that entails “killing”.I agree that in democratic nations people have a “Brahma-Astra” named Right to “anything”, death is something else so right to death is not acceptable.
Another reason it shouldn’t be legalized in India, people will choose to die because they will think of themselves as a burden to the family.So instead of fighting the disease, they will go the other way.Suppose a person is starving for months and you just met him and he is now asking for food, unfortunately, you don’t have anything to feed him.What will you do? Will you ask him to die? OR Will you give him the hope that you can arrange something for him ?.Similarly here we (Society) need to find a way to cure him, it’s our failure that we are not able to cure him.So by any mean Active euthanasia is no different from murder or killing.
One more thing sometimes people think that spending money on such kind of person is waste as they cannot do anything and in many cases cannot communicate too.I believe they can communicate but not the way society so they can do things but not those that society defines “doing”.