Most complex, perhaps, but not "most advanced". I don't think there's necessarily a meaningful "correct" choice for that title, but surely one of the proof assistant languages would be a more likely candidate?
(I don't say this to be disparaging of TypeScript's type system, by any means — it's very interesting stuff!)
(I don't say this to be disparaging of TypeScript's type system, by any means — it's very interesting stuff!)