Being last-ranked is not a guarantee not to interfere with a residency slot. There are many more factors that go into matching.
Being picky on specialty, or location, is going to make a match more difficult. A Competitive specialty like Ortho, Radiology, or Radiation Oncology trying for a big city that is popular would be a hard fit. Due to how few Radiation Oncology programs there are, even a class valedictorian may not get in - there are just not that many slots.
A less desirable specialty like family practice or internal medicine would be a much easier fit for a lower ranked candidate.
Being picky on specialty, or location, is going to make a match more difficult. A Competitive specialty like Ortho, Radiology, or Radiation Oncology trying for a big city that is popular would be a hard fit. Due to how few Radiation Oncology programs there are, even a class valedictorian may not get in - there are just not that many slots.
A less desirable specialty like family practice or internal medicine would be a much easier fit for a lower ranked candidate.