I have thanos 5 stars and 3 stars but sell thanos 3 stars because damage myself … and now thanos dont damage his team. Can i recover it ?
You are probably out of luck, unfortunately.
That said, I once accidentally sold off a cover of a newly released character and Customer Service was able to restore it for me. This was a long time ago and they pointed out that they do not usually do that, but it wouldn’t hurt to submit a ticket asking them nicely and see what happens. Worst that can happen is that they say “no” and you are no worse off than you were before.