step up, snap ya back
Abra looks like a bad gimmick at first glance, but its power relative to the rest of NU is no joke. Base 105 Special Attack is astounding and a base 90 Speed makes Abra one of the fastest threats in the metagame. Combine this with Calm Mind and a great movepool and Abra is a serious offensive threat. Luckily for the rest of NU, its frailty means calling it a glass cannon would be an understatement. Once on the battlefield, something's getting hurt, but consistently getting Abra safely in is tough to do.
name: Calm Mind
move 1: Calm Mind
move 2: Psychic
move 3: Fire Punch
move 4: Substitute / Encore
item: Leftovers / Twisted Spoon / Salac Berry
evs: 4 HP / 252 SpA / 252 Spe
Abra can only come onto the battlefield as a revenge kill, double switch, or through a slow Baton Pass, preferably with a Substitute, but once in there's little in NU that's going to enjoy eating its attacks. Psychic and Fire Punch get the best possible two-move coverage as Fire Punch nails Mawile and Metang super effectively and hits a fair amount of the Dark-types in the tier for good damage. There is a significant level of nuance to playing with Abra due to its frailty; depending on how much of the opponent's team is revealed and chipped, and whether you think the opponent is going to switch or not, should tell you how to proceed with Abra's moves. Calm Mind should be used if you are sure Abra is going to sweep at +1 and if the opponent is going to switch out or can only manage little damage to Abra (the latter being unlikely). Substitute should be used if you know the opponent has a Pokemon faster than Abra and you're sure the opponent will either switch out or not attack Abra. Alternatively, Encore should be used if you're able to get Abra in after the opponent has used a setup or support move and the opponent does not have something faster than it waiting in the wings should they choose to switch out. Finally, Abra should simply attack with the appropriate move if you're sure the opponent will not switch and will attack the next turn.
[ADDITIONAL SET COMMENTS]
A Timid nature and maximum Speed investment is non-negotiable when using Abra as it absolutely needs to outspeed as much as possible due to its frailty and needs to hope to at least Speed tie Venomoth, Vigoroth, and Pikachu should the need arise. The list of customizable moves on this set is nearly endless due to Abra's enormous usable movepool; most prominently is Abra's choice of coverage options. The only move on this set that should never be replaced is Psychic; apart from that, any of the listed moves can be replaced with another of your choosing. Thunder Punch pairs exceptionally well with Psychic as it covers every Dark-type in the tier save for Cacturne and gets a super effective hit on Murkrow and Crawdaunt; however, it loses out on the super effective hit on Mawile and Metang if you use it in place of Fire Punch, both of which are far more common in the metagame. Other coverage options that can be used on this set include Ice Punch, Hidden Power Dark, Thief, and Hidden Power Grass, all of which get better hits on certain targets than Abra's other moves and should be used at the discretion of your team's needs.
Alternatively to a different coverage option is Abra's expansive list of support moves. Thunder Wave and Toxic can be used well from behind a Substitute to cripple certain threats that Abra usually does not fare well against, such as Pidgeot, Flareon, and Kecleon. Taunt has very limited use and requires ace-like prediction, but can be used to severely cripple Sableye and Chimecho. Reflect and Light Screen can be used before Abra bites the dust and provide a safer setup opportunity for a teammate; this works especially well on hyper offense teams. As for item choices, Abra isn't going to get much mileage out of Leftovers apart from allowing it to switch into Spikes and Toxic more effectively, so using a different item is very much a possibility. Twisted Spoon will give Psychic a bit of a boost and guarantees the OHKO on Choice Band Hitmonchan whereas Leftovers has a small chance of missing out. Salac and Petaya Berry naturally pair well with Substitute and can give Abra the boost it needs to complete a sweep; with a Salac Berry boost, Abra is faster than even Huntail in the rain.
Abra works best as either a dedicated late-game sweeper with a team built around it, or as a member of a hyper offense team where it can either wallbreak or sweep depending on the opponent's team. Regardless, Abra begs for slow Baton Pass support to get it onto the field safely. Mawile and Flareon are both great choices for this role and can switch into many of the faster Pokemon that Abra has trouble with, such as Pidgeot and Raticate for the former and Haunter and Plusle for the latter. If at all possible, it is most desirable to remove the opponent's faster Pokemon before revealing Abra, making a phazer such as Wailord a good teammate to reveal as much of the opponent's team before bringing Abra out. Spikes support is fantastic when using Abra, as it can push many 2HKOes into OHKOes, making Roselia and Glalie great teammates. Finally, very specially bulky Pokemon such as Kecleon and Dewgong need to be removed or crippled before attempting a sweep with Abra, making a wallbreaking partner such as Pikachu and Pidgeot a good idea.
A straight all-out attacker set is certainly doable with Abra, as it can be pretty difficult to use its support options effectively. If going this route, a set of Psychic, Fire Punch, Hidden Power Dark, and Thunder Punch will give Abra the best possible coverage against the tier. Abra is one of the few Pokemon with access to Trick in NU and can use it effectively with Choice Band to cripple one of its standard switch-ins such as Flareon, but it can be very difficult to use correctly and Thunder Wave or Toxic will generally be of more help to its team. Other support options not previously listed include Knock Off, Sunny Day, Rain Dance, Safeguard, and Torment, but Abra simply lacks the bulk to use these moves very effectively. Finally, Endure can be used with a Salac Berry and allow Abra to get the jump on many of the Pokemon faster than it, but it too can be very hard to predict correctly and Substitute is generally the safer choice considering Abra's good Speed relative to the rest of the metagame.
[Checks and Counters]
Specially defensive Flareon is probably the safest choice to switch into Abra as it is immune to Fire Punch, is only 4HKOed by an unboosted Psychic, can OHKO back with Fire Blast (or nearly OHKO with Flamethrower), and can heal any damage off with Wish. Kecleon is also an excellent switch-in to any Abra set as it can take advantage of Color Change to make it even harder for Abra to KO it and it will easily OHKO back with Body Slam or Return. Dewgong is the next safest choice and can phaze Abra out with Perish Song or 2HKO with Ice Beam, but it needs to be wary of switching in as Abra boosts with Calm Mind. Chimecho needs to be wary of Taunt and Hidden Power Dark, but offensive sets will easily beat Abra one-on-one even if they get into a Calm Mind war. Sableye with Shadow Ball will easily beat Abra as well thanks to its immunity to Psychic. In the same vein, Murkrow and Crawdaunt will easily beat Fire Punch Abra, although both need to be cautious of switching into Thunder Punch. Finally, Abra is incredibly easy to revenge kill with anything faster, such as Pidgeot and Raticate.