Here are two charts of what Baseball-Reference came up with when I asked it to produce lists of pitchers from 1901 through 2012 who were unlucky in a season.
This image shows the top 11 pitchers who qualified for the league ERA title, had a won-loss percentage of .480 or lower, and had an ERA+ of at least 120:
Note the three pitchers from 2010 through 2012. It’s hard to say who was the unluckiest pitcher of the 11, but boy, Turk Farrell’s 10-20 in 1962 does stand out.
This image shows the top 11 pitchers who qualified for the league ERA title, had five or more shutouts, and won 15 or fewer games:
Rube Waddell’s 1906 and Jon Matlack’s 1974 show up on both lists, so you could say they had the unluckiest seasons ever (or at least since 1901). In 1977, Tanana led the A.L. in ERA, 2.54, and ERA+, 154. How did the Angels, with Tanana and Nolan Ryan, fail to even win the West once before 1979?