I know many will disagree, but I feel that all the worst syntax mistakes from C/C++ are there.

It's uneasy to spot declarations:

  Point p {1,2} // declaration
  Point {1,2} // expression

Semicolons are sometimes required, sometimes not:

  class C { ... }
  struct S { ... };

I despise the use of <...> as a type of parentheses, as if the < and > symbols were not enough overloaded.

And finally, probably it's my problem, I really really hate the :: symbol.