I find my 58 year old eyes struggle with the sights on a variety of the surplus service pistols I own. I have an occupation FN 1922 in .380 that I find especially challenging. The trigger, grip, tiny sights and snappy nature of the .380 round in this gun all combine to make it tough to shoot well.. I'd say my Inglis Hi Power would be a runner up. Once again, I find the sights and trigger make it difficult to shoot decent groups.
In both cases though, I think a goodly portion of the problem is me rather than just the gun.