I think I've found the Pokemon that can beat anything on that list;
The level 40 Houndoom from Inlet Grotto. I once started a new
savefile just to check what it can do and it is able to crunch
oneshot a level 100 Pokemon, that is also quad resistant to dark. I
didn't try using a focus sash, but it most likely just breaks
through it. That Houndoom is a dirty hacker.
"What you do with the gift of life determines who you are"
- Mewtwo