You asked
Sigma 85mm f 1 2 dg art vs samyang af 85mm f 1 4 fe ii?
The Sigma 85mm f/1.2 DG Art is the one for you if you want the shallowest depth of field and the fastest light. It's Sigma's flagship portrait prime, and it mounts on both Sony E and L-Mount. Wide open, it gives the most separation between subject and background, though it's a big lens to carry.
The Samyang AF 85mm f/1.4 FE II is the sensible choice if you shoot Sony E and want the classic 85mm look without the extra stop of speed. It's made for full frame and autofocuses, but it's Sony E only.
Neither lens is stabilised, so keep your shutter speed up. For more on how an 85mm suits people, see portraits, and for the wider picture, see lenses.
Written by Claude from this site's pages.