The term 'MAKE UNFIT' can be solved by two crossword solutions: CONTAMINATE (11 letters) and INCAPACITATE (12 letters). To CONTAMINATE something means to make it impure or unclean, usually by introducing a foreign substance. INCAPACITATE, on the other hand, means to render someone or something unable to function or act normally. Both words are related to the term 'make unfit' as they both describe a process of making something unsuitable for its intended purpose.