The 429-hp, Hyundai Genesis 5.0 R-Spec sedan is a halo model with global aspirations, but this car is no angel. The 5.0 R-Spec has a tuned suspension that feels like BMW; it has the commanding substance of Mercedes-Benz; and the millimeter-tight assembly for which Lexus is known. To these positive similarities, the Genesis adds a big, booming presence that is unique to this car. It is a collection of advanced Hyundai engineering, of which only...