The really offensive enemies are the tutorial ship's mind flayer and Commander Zhalk. We should be absolutely obliterated if we try to fight them. The Mind Flayer should Mind Blast us (60 foot cone, DC 15 Int ST or take ~22 damage and get stunned if you somehow survive it), since it would be simple to get both us and Zhalk in the same blast. Idk about Zhalk but I assume he, as a seemingly powerful individual, should also have something similar.
But the fact that it's fairly feasible to win that combat just makes a joke of all "powerful" enemies. The mind flayers seem like they're supposed to be (one of the) Big Bads of BG3. So let them be a Big Bad. There should be enemies we can encounter that it's nearly impossible for us to defeat.
As for the rest of the enemies, eh the only other one that's potentially a problem (as others have said, Drow are CR 1/2, Duergar are CR 1, and even Minotaurs are only CR 3; all perfectly reasonable enemies for level 1-5 characters) is the red dragon. If you attack the red dragon before it flies off, it should also obliterate you.
