Harassment from neighbor

Dear Sir, Im the owner of flat no E2406 in Aparna Sarovar Zenith , Hyderabad . I gave the flat for tenancy and currently the tenant is residing in the flat. The problem is that the tenant is harassed by the neighbor residing in the below flat E2306. The neighbor alleges that my tenants kids are making noise and my tenant refutes it. My tenant says that the neigbor is annoyed when anyone walks in the flat, let alone making noise . My tenant complained to the association , and the association tried their best to amicably settle the matter , but to no avail as the neighbor doesn't budge. There's also general.opinion about this neighbor amongst the apartment security agency and few other residents that he's quite psychotic. Now, my tenant wants to vacate the flat because of the harassment and he's also afraid that the neighbor could harm his family. I can put the flat for rent , but I'm also afraid that the if the neighbor metes out same behavior to new tenants and he continues the harassment to make the new tenants also leave the flat. Request you to kindly provide me the due course to come out of this menacing situation.