I think Russian Tair 11A (135mm f2.8) has something close to 20 blades.
Jupiter 9 (85mm f2) has ... 15 blades ...
They are M42 mount.
Tair 11A is one of the best Russian lenses I had.
FYI, if you look for old lenses in pre-set aperture, they usually have too many blades to count ...