Onix would work just fine, the main thing is the sturdy. Abra will almost ALWAYS use dark pulse on gardevoir, magnezone, and escavelier.
Train escavelier to level cap, he MIGHT be able to tank 1 hit and get an attack off
At the flower shop in lapis? ward you can get a free fairy type, abra will use hyper beam on that 90% of the time
Get an onix, and train it to at least 31 so that it learns screech (harshly lowers defense). It will be able to get 1 screech off gauranteed due to sturdy
Catch a magnemite in shade's factory until you get one with sturdy (they can have it)
level it to somewhere in the 30s so it learns screech
use both of the screeches to pretty much floor the abra's already lowish defense.
Send torterra out, and get one EQ off, it should deal a LOT more damage now, because it hits physically
Once it dies, send the fairy type out, and pray to RNGesus that abra uses hyper beam
While abra is recovering, send Escavalier out and 1 shot that little bugger with X-Scissor, Escavaliers high attack and abra's now-super-low defense should let you kill it.
If abra uses hyper beam anywhere above, like on onyx, get another screech off. If he uses it on torterra, get another EQ off. You should be able to kill him with that strategy, if that doesn't work tell me and we can think of something else
P.S. If magnezone knows screech, you can use an ability capsule (maybe?) to give him sturdy. That's your choice though