Is it bad practice to pass a fragment in as an adapter's parameter so you can access it's methods?

Yes, but what exactly do you want from a fragment inside a adapter?

I want my recyclerview to access the same viewmodel as my fragment

That sounds highly suspicious

My viewholder class is handling a lot of logic for the view items, 400 lines of code worth. I'm trying to think of a way to have some seperation and clean up this class. I'm using mvvm and have a viewmodel for my fragment already. I figured one solution was to move some of the functionality to that same viewmodel

You can use the Rx kotlin or Rx java to do that. No need to pass the fragment.

View related logic is fine to have in the holder but you should try to extract all the other logic into the

viewModel

.