Physical set
Empoleon (F) @ Life Orb
Ability: Defiant
EVs: 252 Atk / 252 Spe
Adamant Nature
- Waterfall
- Drill Peck
- Earthquake
- Swords Dance
Waterfall - STAB, good power, chance to flinch foe.
Drill Peck - Good power, covers weaknesses.
Earthquake - Great power, covers weakness.
Swords Dance - Sharply raises attack.
This set is pretty legit. It does some serious damage, pretty standard but effective, all weaknesses covered. Plus, Empoleon is pretty sturdy, so this allows the user a turn to set up at least. It makes for a pretty powerful Empoleon.
OR
Special set
Empoleon (F) @ Wise Glasses
Ability: Torrent
EVs: 252 SpA / 252 Spe
Modest Nature
- Scald
- Hidden Power [Ground]
- Ice Beam
- Flash Cannon
Scald - STAB, good power, and a chance to burn the foe.
Hidden Power [Ground] - covers weaknesses.
Ice Beam - Coverage and good power, and a chance to freeze foe.
Flash Cannon - STAB, good power, and a chance to lower foe's Special Defense.
This set works well too, though you might have a problem against Fighting types. If trained properly, you could probably knock out the Fighting Pokemon in a shot, as most Fighting Pokemon have atrocious Special Defense stats.