Korean word segmentation using frequency heuristic
It will be much faster to use Python's in operator for your substring search rather than using your custom-built "contains" function.

In [15]: %timeit 'brown' in  'blah'*1000 + 'the quick brown fox'
100000 loops, best of 3: 2.79 µs per loop

In [16]: %timeit contains('brown','blah'*1000 + 'the quick brown fox')
1000 loops, best of 3: 870 µs per loop


Also I wonder if you could rewrite some of your custom functions as dictionary comprehensions, something like this:

for word in read_words(args.wordlist):
    combos = {k:v for k,v in corpus if k in word}
    results = {'Original': word,
               'Pois': list(combos.keys())
               'Makeup': combos.items()
               'Freq_Max_Delta': sum(combox.values())}

    print(results)