The Eilish siblings’ writing and production style is certainly unlike anything we’ve heard in recent mainstream hits, and Bad Guy is no exception. The song uses a variety of interesting vocal production techniques, including a stuttered vocal transformer effect and relatively dry, intimate vocals (as opposed to the more prominent reverb heard in most Pop songs), as well as pitch-shifted laughter and distorted breath sound effects. The song also contains several interesting compositional characteristics such as a highly differentiated bridge that turns the song on its head from danceable Indie Electropop to aggressive Trap, and multiple turnarounds that provide engaging contrast over the course of the song. However, despite its highly unique elements, other elements such as Bad Guy’s K.I.S.S. ME melody (Keep It Simple, Singable & Memorable), effective rhyme schemes, and an infectious combination of instrumental and vocal hooks give it the mainstream appeal it needed to easily connect and resonate with widespread audiences.
Source: Hit Songs Deconstucted