The phrase "complete mismatch" means that two things or people are completely different and do not go well together or do not fit together at all. Full definition
Werdum's on a bit of a skid beside some wins over complete mismatches (Marcin Tybura, Walt Harris, Browne) and lost to every contender hes fought since Stipe. (sbnation.com)
The difficulty for me comes in the fact that my employment for the past 20 has felt like a complete mismatch. (nakedpastor.com)