From the look of the new Type Chart, it seems as if the old combination of Earth, Steel, Dark, and Sound Type moves still stands as the reigning champion in terms of super-effective mono-type coverage, hitting 13 of the 17 base types for super-effective damage, including the new type that was introduced (which is weak to Sound Type moves). However, it seems as if this combination has a couple contenders. For example, a combination of Earth, Electric, Dark, and Sound Type moves have the same amount of super-effective coverage (since Electric Type attacks now hit Sound Type Puppets for super-effective damage), as does a combination of Earth, Electric, Dark, and Fighting Type moves (since the new type is also weak to Fighting Type moves, which now tie with Earth Type moves for most individual super-effective coverage, though both are super-effective against Steel Type Puppets).
Honorable mentions go to the following move combinations, which can hit 12 of the 17 base types for super-effective damage:
Earth, Steel, Dark, Wind
Earth, Steel, Dark, Nature
Earth, Poison, Fighting, Wind
Earth, Poison, Fighting, Dark
Earth, Poison, Dark, Chaos(?)
Earth, Electric, Fighting, Illusion
Earth, Electric, Light, Sound
Fighting, Poison, Dark, Wind
Fighting, Electric, Dark, Sound
Poison, Dark, Wind, Chaos(?)
Any others that I missed?
