Sceptile has the best movepool, in terms of both coverage and power. Access to Swords Dance boosts its base 85 attack, good 120 speed and also 105 sp. atk if you decide to give it a special set.
Physical moves
Leaf Blade
X-Scissor
Acrobatics
Drain Punch
Earthquake
Rock Slide
Thunder Punch
Low Kick
Crunch
Brick Break
Special moves
Leaf Storm
Giga Drain
Focus Blast
Solar Beam
Dragon Pulse
Status/ other moves
Synthesis
Leech Seed
Agility
Sceptile has more moves, but I listed the ones that you would actually consider using in competitive battle.
Essentially, Sceptile's physical movepool covers all of its weaknesses. Rock Slide covers Flying, Bug, Ice and Fire, Earthquake covers Poison, but also Steel which its STAB grass is x1/2 against. Leaf Blade for consistent STAB.
Physical set
Sceptile @ Life Orb
Ability: Overgrow
EVs: 252 Atk, 252 Speed, 4 HP
Nature: Jolly
- Swords Dance
- Leaf Blade
- Rock Slide
- Drain Punch/ Earthquake
Mixed set
Sceptile @ Life Orb
Ability: Overgrow
EVs: 180 Atk, 72 Sp. Atk, 252 Speed, 4 HP
Nature: Hasty
- Lead Storm
- Rock Slide
- Earthquake
- Drain Punch/ Leaf Blade
Sceptile's special movepool isn't that great, so mixed set is my advice if you want to use Leaf Storm.
Also Unburden as an ability would be nice, but as its not released yet for Sceptile, we'll have to do with Overgrow.
Downside: Sceptile is not suitable for taking hits, with base 70/65/85 in its defences. You'd have to time your switch-in well in order to allow it to set up swords dance safely.
