Perhaps best known from
The Good, the Bad and the Ugly, Lee Van Cleef was a sought-after actor in westerns in those days.
Unfortunately, it didn't last, and in the 1980's he ended up doing a humiliating turn in the TV series The Master, which was spoofed on MST3K in a version which combined two 1-hour episodes of The Master into a single feature film with a complete plot change in the middle.