Taking Alakazam! This had a lot of the stuff it needed already, so I basically just emphasized current threats more (ScarfMoxieMence) and fleshed it out a bit.
original
The best way to get by Alakazam is simply by exploiting its frailty, eliminating it before it does major damage. Attempting to outrun Alakazam is a challenge due to its base 120 Speed, so foes will typically resort to Choice Scarf and priority users, mainly Scizor and Mamoswine. Sets utilizing Focus Sash or Substitute, however, thwart such solutions, while bulkier opponents will struggle against sets with boosting moves or items. The most general counters are those that Alakazam can't 2HKO instantly; Jirachi is a common example of this, capable of setting up with Calm Mind or threatening with paralysis. Both Sableye and Spiritomb are immune to Psychic and Focus Blast, and only neutral to Shadow Ball, giving them time to KO Alakazam before being KOed themselves. Other examples of bulky and powerful Pokemon that could take down Alakazam include Scizor, Metagross, and Bronzong. If Alakazam lacks Psyshock, it obviously has trouble getting past special walls, though at this point, we've reached the bottom of the barrel. Generally speaking, if Alakazam can't immediately outspeed or eliminate a threat, you can expect the frail magician to go down quickly and quietly.
<p>Alakazam generally has to rely on its high Special Attack and Speed to beat down most of its threats; consequently, Pokemon that can either sponge hits from Alakazam or outspeed it have a good chance of beating it down. Some dedicated specially-based walls, such as Blissey and Chansey, cannot effectively beat Alakazam due to Psyshock's effect of hitting the opponent's Defense instead of its Special Defense. However, walls that resist Alakazam's STAB and have the bulk to switch in to Life Orb-boosted Focus Blasts do well, especially Jirachi and to a lesser extent, Bronzong. Jirachi can threaten to set up a Calm Mind or paralyze either Alakazam or its teammate that switches in, and Bronzong can simply hit hard with Gyro Ball. Speaking of paralysis, it is a great way to take Alakazam out of commision. If one is able to paralyze Alakazam, it loses out on its biggest asset, its humungous base 120 Speed.</p>
<p>Rather than walling Alakazam, the easiest way to combat it would be revenge killing it due to its frail defenses. While this may seem tough to accomplish, especially considering the high base Speed of Alakazam, most common Choice Scarf users outspeed it. Choice Scarf Rotom-W, Landorus, Terrakion, Latios, Hydreigon, Salamence, Politoed, and Jirachi will all outspeed and either OHKO or 2HKO Alakazam with ease. Additionally, using priority moves is an easy way to keep the moustached magician in check, as it can rarely survive a strong attack. Choice Band users such as Scizor, Dragonite, Metagross, and Azumarill can easily dispatch Alakazam, though they will not enjoy being hit themselves if Alakazam carries a Focus Sash.</p>
<p>Pokemon that are immune to Alakazam's main coverage moves, Psyshock and Focus Blast, can usually take Alakazam down. Sableye and Spiritomb can both sponge a Shadow Ball and KO it back with their Dark-type STAB moves. Should Alakazam choose to carry Psychic instead of Psyshock, Blissey and Chansey, among other specially-based walls such as Gastrodon, will be able to sponge hits and recover off damage, eventually stalling Alakazam out, or simply KOing it. However, they cannot effectively beat Calm Mind sets, so one must be wary of accidentally sending out setup fodder.</p>