As a general rule all the SMCP (K) lenses are as sharp on the K-1 as they were on film. The best of them are stellar lenses on K-1. IMO K28/2, K28/3.5, K35/3.5, K50/1.4, K55/1.8, K85/1.8, K105/2.8 are sharp enough to outresolve the sensor, not to infer the others are soft. Others can chime in. You can see from the link in my signature I own almost all of them.
Note that these are in many cases the S-M-C or SMC Takumar lenses remounted in K-mount. They render a bit warmer than M and A lenses and they are designed to an earlier film era taste for sharp centers and softer edges to promote the center subject of the image. If you are looking for the modern, clinical edge-to-edge sharpness you might be disappointed.
Review the later pages of the
K Club. Many of those images were shot on K-1.