You asked
Is the tokina f rin 20mm f 2 fe af worth buying used?
I'd say yes, as long as you shoot Sony E and want a wide prime. The site doesn't list prices, so compare any used offer with what a new one would cost. Lenses hold their value well, and buying used is one of the best ways to afford good gear.
This is a full frame lens, so it suits a full frame body such as the Sony a7 III or Sony a7 IV. On an APS-C body like the Sony a6400, it frames like 30mm on full frame, which is much less wide. It isn't stabilised, so check the used copy's focus and glass carefully before you pay. The full specs are on the Tokina FíRIN 20mm f/2 FE AF page.
Written by Claude from this site's pages.