The latest update of Lemmy added in a system that allows admins to deanonymize the votes on a comment in cases where there's blatant vote abuse, so you can probably ask @dessalines where it's coming from so that they/you can deal with it. I'm sure with time better systems will be put in place but for now this is the best tool you have to fight back against this sort of trolling behavior.
For example before I was banned from LemmyWorld they would constantly barrage my posts deep into the negatives whenever I posted anything left of center, and it would be nice to be able to break down the voting scores among each instance so that one ideology doesn't just take over and become representative of the entire federation. From what I heard, Hexbear literally had to disable downvotes completely because LW reactionaries would slam every single post and every single comment they saw there, to the point it actually damaged their culture. The only way to defend against this is to either defederate entirely, or to ask the admin of the problem instance to ban you (so your posts stop showing up to their users) and if they're a bad faith nazi instance (like sh.ithole) they can just say no.