Has anyone been successful with a nuisance eviction in Erie County, NY where a tenant has damaged property, committed crimes, harassed another tenant, etc?

Unless she has filed something with the police saying he is harassing her or something I would think she is responsible. 

I'd try and not let it bother me and build a taller privacy fence for the backyard to prevent her from stick her head over the fence to harass your tenants.

The bad news is that the HOA fees can increase and kill cash flow, the quality of the HOA is entirely dependent on the HOA Board and your neighbors, and you may have a retiree (or many) that spend their days harassing you or your renters over ridiculous rule violations.I personally wouldn't invest in one because of the negatives, but everyone has their own threshhold of pain.

Not much advice here but I’d say save all those messages this guy is sending and turn them over as evidence of harassment if you can.  

You may also want to add a harassment complaint to reduce the stress. 

I would have liked to be even 25% partners on the buy and holds I helped acquire and rehabbed to rent status .. but that realtor got into his head .. when I confronted her on it , she accused me of sexually harassing her .. ( she’s a piece of work .. and she’s doesn’t like men ..as in , she’s in a relationship with a woman .. even if she didn’t look like a man ) I would never sexually harass anyone  ! 

It just is kind of harassing and I'm not sure what to do at this point.

The neighbor on one side has been harassing them for some time, shouting homophobic slurs and insults, throwing trash in their yard and such. 

There is such a thing as phone harassment.