MOND famously (notoriously?) cannot explain the observed motions of galaxies within groups and clusters (the oldest known evidence for dark matter). Even if you assume MOND is true, the galaxies are moving too fast, so you need an extra source of, well, dark matter.
It's often said that mind has difficulty explaining bizzare galaxies but my understanding is that's not true. I thought the only thing that MOND cannot explain is the matter distribution in the early universe, which requires an anisotropy that MOND does not "give for free" like dark matter does.