Standard Specs Swellow. Nice revenge killer, that can also function as a late game sweeper. Normally Heat Wave is a must have, but with Probopass around, it opens up either Sleep Talk, or Brave Bird as a possibility as well. Sleep Talk helps deal with the likes of Vivillon, and Lilligant.
4 Atk Swellow Brave Bird vs. 0 HP / 4 Def Hariyama: 338-402 (78.7 - 93.7%) -- guaranteed 2HKO
On the analysis, there is only Specs Altaria listed. I wanted a bulky, non-AV set, so I came up with my own spread. Note that I am badly and the calcs that I did when I came up with the set were without Leftovers (whoops), so just assume they were Knock'd Off or something.
252 SpA Choice Specs Pyroar Hyper Voice vs. 248 HP / 176+ SpD Altaria: 144-171 (40.7 - 48.4%) -- guaranteed 3HKO
252 SpA Life Orb Haunter Sludge Bomb vs. 248 HP / 176+ SpD Altaria: 130-153 (36.8 - 43.3%) -- guaranteed 3HKO after poison damage
252+ SpA Magmortar Thunderbolt vs. 248 HP / 176+ SpD Altaria: 78-92 (22 - 26%) -- 6% chance to 4HKO
252 SpA Choice Specs Swellow Boomburst vs. 248 HP / 176+ SpD Altaria: 141-166 (39.9 - 47%) -- guaranteed 3HKO
136+ Atk Steelix Heavy Slam (120 BP) vs. 248 HP / 44 Def Altaria: 151-178 (42.7 - 50.4%) -- 1.2% chance to 2HKO
+2 252+ Atk Sceptile Rock Slide vs. 248 HP / 44 Def Altaria: 280-330 (79.3 - 93.4%) -- guaranteed 2HKO
252 SpA Life Orb Sceptile Hidden Power Ice vs. 248 HP / 176+ SpD Altaria: 218-260 (61.7 - 73.6%) -- guaranteed 2HKO
40 SpA Altaria Dragon Pulse vs. 0 HP / 4 SpD Haunter: 117-138 (50.6 - 59.7%) -- guaranteed 2HKO
40 SpA Altaria Flamethrower vs. 244 HP / 128 SpD Steelix: 124-146 (35.2 - 41.4%) -- 72.1% chance to 3HKO after Leftovers recovery
40 SpA Altaria Flamethrower vs. 252 HP / 4 SpD Eviolite Ferroseed: 156-184 (53.4 - 63%) -- guaranteed 2HKO
Note that Altaria allows Sceptile to get cleaned off by Swellow, which doesn't OHKO Sceptile I mean, Brave Bird probably does, but it lives a Boomburst. And yes, I am aware that Sceptile may very well be banned in like 2 weeks. Spreads not perfect, but it looks decent enough to me.
Probopass is Magnet Rise to better check things like Steelix. Magnet Pull helps it handle some things Swellow might not appreciate late game, and it has a great type synergy with Altaria as well. It also sets up Stealth Rocks, and a slow Volt Switch may come in handy for allowing Swellow to get a kill here and there. I just used a 252/252 spread, since I couldn't think of anything it specifically wants to check that it may need investment in SpDef for. I suppose you could try to add Pain Split onto Probopass for longevity, but that requires getting rid of some other move, and 4 move slot syndrome is never fun.