I've said it time and time again, +6 is stupid. You're not getting there, period.
But in the interest in maybe getting something else done... lets take a different route. Do you really thing that (lol) +6 Aegislash is the best endgame sweeper in the current metagame? In a game surrounded by Mega-Lucario, Scizor, Mega Mawile, Mega Absol, and other forgotten relics of past generations (CB Technician Hitmontop, Fake Out Technician Ambipom).
If your team is built around an endgame priority sweeper, why not use the best one? Life Orb Scizor (potentially now... Mega Scizor) is the most obvious choice.
Note: Lucario, Absol, Scizor, and Mawile all have access to the deadly Swords Dance + Priority combo. Aegislash is
hardly alone in this market. Scizor and Lucario serve as perfectly good non-Mega priority sweepers as well.
So lets do a bit of damage comparison, now shall we? I chose Dragonite, because it takes neutral damage to all of these attacks.
- 252+ Atk Life Orb Technician Scizor Bullet Punch vs. 252 HP / 0 Def Dragonite: 146-173 (37.82 - 44.81%) -- guaranteed 3HKO
- 252+ Atk Life Orb Lucario ExtremeSpeed vs. 252 HP / 0 Def Dragonite: 117-138 (30.31 - 35.75%) -- 36.77% chance to 3HKO
- 252+ Atk Life Orb Deoxys Shadow Sneak vs. 252 HP / 0 Def Dragonite: 109-130 (28.23 - 33.67%) -- 0.24% chance to 3HKO
I assigned "Deoxys" ghost typing, and he serves as a good Aegislash proxy because of his 150 base attack.
Advantage: Life Orb Lucario. With 90 base speed, Lucario outspeeds major bulky threats like Dragonite and Gyarados, and can simply resort to Ice Punch, Stone Edge, Earthquake, or Close Combat. Extremespeed does more damage than Aegislash, and with access to Swords Dance and better attacks (ie: Close Combat, Earthquake, etc. etc.), Lucario is still a better endgame sweeper than Aegislash.
Scizor of course gets his own mention, as his Bullet Punch is one of the strongest non-Mega non-Uber priority attacks in the game.
Speaking of Megas, lets see what happens when Mawile and Absol hit the field. Again, all of these pokemon have Swords Dance to threaten a "priority sweep".
- 252+ Atk Life Orb Arceus-Normal ExtremeSpeed vs. 252 HP / 0 Def Dragonite: 185-218 (47.92 - 56.47%) -- 84.77% chance to 2HKO
- 252+ Atk Huge Power Mawile Sucker Punch vs. 252 HP / 0 Def Dragonite: 172-203 (44.55 - 52.59%) -- 21.48% chance to 2HKO
- 252+ Atk Absol Sucker Punch vs. 252 HP / 0 Def Dragonite: 168-198 (43.52 - 51.29%) -- 5.86% chance to 2HKO
- 252+ Atk Technician Scizor Bullet Punch vs. 252 HP / 0 Def Dragonite: 126-148 (32.64 - 38.34%) -- 99.15% chance to 3HKO
- 252+ Atk Adaptability Lucario Bullet Punch vs. 252 HP / 0 Def Dragonite: 110-130 (28.49 - 33.67%) -- 0.37% chance to 3HKO
- 252+ Atk Life Orb Deoxys Shadow Sneak vs. 252 HP / 0 Def Dragonite: 109-130 (28.23 - 33.67%) -- 0.24% chance to 3HKO
Mega Luke and Mega Scizor don't hit as hard without Life Orb, but they still are better than Aegislash's unboosted Shadow Sneaks. Even then, Lucario is going off of 112 base Speed and a Base 240 Close Combat, Lucario arguably doesn't need Bullet Punch / Extreme Speed anymore to sweep.
Mega Scizor has 70 / 140 / 100 defenses, and is NOT Earthquake weak. Mind you, in "priority sweep mode", Aegislash only has 60/50/50 defenses. If any opponent survives (focus sash, unexpected bulk, etc. etc.), Aegislash dies after the Shadow Sneak.
The other megas: Mega Mawile and Mega Absol are quite different of course... their priority damage output is roughly on the order of Arceus-Normal ExtremeSpeed... at a downside that it can (and probably will be) predicted. Nonetheless, they represent an unprecedented amount of power in the OU Metagame.
Mega Absol may not be quite as strong as Mawile (despite the STAB advantage, Mawile still boosts dmg over him). However, Mega Absol is rocking Sucker Punch / Pursuit / Passive Magic Bounce off 150 Atk and 115 Base Speed. Now THAT is what I call a mind game: guess wrong and you die.
Say what you will about Aegislash. If Aegislash really requires lol +6 to sweep with a priority attack,
get a better sweeper. Scizor doesn't require it, because he's bulky enough to survive. Lucario doesn't require it, because +2 Adaptability Close Combats OHKOs damn near everyone and 112 Base Speed pulls it off easily. Finally, Mega Mawile and Mega Absol are nearly twice as powerful as Life Orb Aegislash, so their +2 does the same damage as Aegislash's +6.
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So what does Aegislash offer to the table? Is he packing the movepool of Lucario / Scizor? Does +2 Sucker Punch OHKO Garchomp like Mega Mawile / Mega Absol can? Is he rocking Absol's Pursuit + Magic Bounce for some crazy mind games?
Does Aegislash have 112 speed (like Lucario?), does he have 115 speed? (like Absol)? Does Aegislash outspeed anybody... at all?
Listen: No one sweeps with a 40BP attack... and no one sweeps with 60 base unboosted speed. Its just not tactically sound. If you want to run Aegislash as a sweeper, spend a turn setting up Automatize and let him sweep from there.
But really, this "get to +6" idea needs to stop. It simply doesn't happen in high-level play... mostly because other tactics are just straight up superior.