Pokémon X and Y Walkthrough, Pokémon Move Sets: Scyther
(Please note that the recommendations below are largely made for in-game play. A Scyther in a competitive environment will likely make use of different moves to accommodate for smarter, more adaptive opponents. Got an alternate strategy for your Scyther? Let us know in the comments.)
One of the oldest pokémon on the books, Scyther remains a staunch fan favourite. It looks cool, it works well, and it's one of very few pre-evolutionary pokémon that is arguably as good as its evolution, Scizor. It may not receive a fancy Mega Evolution, but Scyther is one battler that means business.
Type: Bug / Flying
Getting a Scyther on its own is easy enough - you just have to catch one. That said, Scyther can evolve into a Scizor if you trade it with a Metal Coat attached. Do that and it will shift forms when it arrives on the other end. (We're not worrying about Scizor in this article, though.)
Bug, Fighting, Grass. Immune to Ground.
Electric, Fire, Flying, Ice, Rock (4x).
Unlike most preevolution pokémon, Scyther easily has the stats to make it into a powerful pokémon of its own accord. Its HP, Defense and Special Defense are all in the good range, though nothing stellar, while its Special Attack droops well below average. These stats aren't all that important to a strong Scyther, though - instead, it's Attack and Speed where Scyther shines. It's excellent at both, allowing Scyther to outrun most pokémon and slice them up when it goes first. There are faster and stronger pokémon, but Scyther can hold its own.
Swarm: If the pokémon is reduced to one third of its total HP, its bug-type moves gain a substantial boost in power. This is a decent ability for a defense-minded Scyther carrying an Eviolite, but sweeping Scythers will have little use for this ability. The average Scyther that gets hit will also go down, thanks to its wide range of weaknesses.
Technician: Moves with an attack power of 60 or less will receive a fifty percent boost to their attack power. This is an amazing move for Scyther, allowing several normally subpar STAB moves to become substantially stronger. I highly recommend sticking with a Technician Scyther.
Steadfast: The pokemon's Speed increases for the duration of the battle whenever it flinches. You generally want Scyther to go first anyway, so this isn't that great an ability. Nevertheless, Steadfast isn't bad. This is a hidden ability.
Your standard sweeping Scyther, preferably one with Technician, will lean towards a variety of attacking moves. Aerial Ace is a fantastic STAB move that will negate attempts at evasiveness, receiving a heart boost to 90 attack on a Technician Scyther. If you can get it (haven't personally, yet), Bug Bite is another great Technician move, and better at psychic-type killing than the naturally-learned Night Slash. If you can't get Bug Bite, U-Turn is a great way to keep your Scyther safe while still doing substantial damage before a switch. You can also drop a non-STAB move on your Scyther; I like Return, personally, though it depends on what you need. Beyond that, Swords Dance, Agility, and / or both are good options. I especially recommend Swords Dance if you equip your Scyther with an Eviolite and are capable of withstanding the first hit on your pokemon.
EV / Super Training
Attack and Speed. Scyther is pretty hefty in both categories, and they should be maxed out before you focus on anything else. You can boost its defenses, which will improve survivability, but at the cost of killing capacity. If you do bother to boost Scyther's defenses, make sure to equip it with an Eviolite to turn it into a surprise tank. (Indeed, you should probably equip Eviolite no matter what. It's not often that you get to use a pre-evolved pokémon that's as strong as evolved pokémon on its lonesome.) HP's importance is meh; Special Attack's is even more negligible.
Catching a Scyther
Scyther isn't too difficult to catch, though you'll have to wait a while in Pokémon X and Y, as it only appears on Route 21 - the second last Route in the game. It appears on its own and in hordes.