The suffix in the word "disqualification" is "-tion".
A suffix is a morpheme added at the end of a word. Moreover, a suffix generally consists of a group of letters and it makes possible to form new words, also called derived words. In that way, sometimes, suffixes can also change the meaning of a word, add more information to that word and even modify its function. For example, it is possible to transform a verb into a noun just by adding a suffix at the end of a word. Some of the most common suffixes besides "-tion" are "-ed", "-er" and "-ity".