There is nothing you can do. You've already screwed up.
This is what you should have told them instead.
"I'm sorry, but I can not in good conscience forward a private
communication sent to me from another potential employer."
Please note the purposefully vague language I'm using here. It's
important to not even disclose the name of company A (unless you
already did). If they ask, just tell them what the company does in the
most general terms, so that they know the kind of company that they're
up against, but you certainly don't need to be specific.
And yes, it's company B's prerogative to decide whether you should
become their employee or not, so they could very well deny you the job
on the grounds that you didn't forward that offer letter to them
(which is well within their rights). But at some point, you have to
respect yourself enough and be willing to walk away from a potential
employer that is making a seemingly unreasonable request.
And what happens if company B doesn't
believe that you have an actual offer on the table from another
company since you're unwilling to show an offer letter? That's fine
also. If they don't believe you, that's on them. And it's not your
obligation to justify, or explain yourself further, and it's your
prerogative to be able to walk away from any potential employer,
especially any potential employer that makes seemingly unreasonable
and unusual requests.
Taken from my previous answer:
Can one company ask offer letter of another company
Now the only thing you can do is to continue looking for a new job with other employers.
I ended up nothing in hand :( What should I do? Can I file complaint against him or his organization?
No, a complaint won't get you anywhere (unless India has a law like the European GDPR as John Bentley suggested).
One thing you could do is post a complaint about company B on glassdoor.com (or the equivalent web site in your country), but personally, I definitely wouldn't post a complaint on glassdoor about company A. You were in the wrong with company A. You broke the implied confidentiality of their offer letter.
That being said, this does not constitute legal advice. I am not a lawyer. And most of us on this stackexchange are certainly not familiar with the law in India. So take our uninformed opinion for what it's worth. And don't be afraid to consult an employment lawyer in your jurisdiction if you can afford it, or if their initial consultation is free.