Medical Return is a decent reincarnation story with a believably overpowered protagonist: instead of superpowers, he has a lifetime of medical experience and training.
Some weaknesses of the story:
The main antagonist is depicted a bit weirdly (he gets screwed over by his upbringing, then once more by the protagonist's reincarnation). There's a love triangle that takes too long considering how little it ultimately matters. There's at least one case of a literal deus ex machina (c87). And crucially, while there's lots of medical terminology, you rarely ever see medical techniques actually performed - at the very least, scenes in the operating room almost entirely focus on the doctors, rather than on the surgeries.
Also, the antagonist continually commits crimes, but no-one can do anything because "there is no evidence". So they're all supposedly perfect crimes, but the story never puts in the effort to show how the antagonist could possibly accomplish them. (Contrast this with Monster, which goes to great lengths to show just that.) And yet the very same criminal continually drops suggestive hints in his conversations. So he leaves no evidence so he won't get caught, then gives hints so he will get caught?_?
And finally, there's a brief Americans-hate-foreigners or Americans-are-racist story arc. This is not the first manhwa to do this, and I just find the trope tiresome. I'm skeptical whether Asian countries are any better in this regard, and would furthermore claim that the existence of this story arc and how it depicts people from another nation is evidence to the contrary. (Speaking as someone who's from another continent altogether.)