Shadow Aggron

Shadow Aggron is... fine. Given the right matchup, it can be hilariously bulky, and the Shadow Boost makes it able to actually hold its own DPS-wise, but it's still a lesser pick for the majority of raids. Raising one isn't a bad thing, but it's also not an amazing investment, either.

Best PvE Offensive Moveset

• Iron Tail shares typing with Heavy Slam to fulfill a niche Steel-type role.
• Smack Down pairs well with Meteor Beam if Aggron is ever needed for Rock-type coverage. 
• Stone Edge is worse than Meteor Beam.
• Rock Tomb is a downgrade. 
• Dragon Tail doesn't get STAB, and consequently performs worse. 
• Don’t use Thunder on offensive Aggron.

Best PvE Defensive Moveset

• Iron Tail usually beats Dragon Tail on defense due to STAB, but they are close.
• Smack Down gets STAB and offers more coverage, but is resisted by Machamp. 
• Rock Tomb is quite slow and lacks damage, making it poor for defense despite being a 2-bar move. 
• Heavy Slam is a 2-bar Charge Move and can be tricky to dodge.
• Meteor Beam is strong and has a fairly early damage window, but it is a 1 bar move and is inconsistent at lower motivations.
• Stone Edge is very hard to react to, but a demotivated Aggron will struggle to use it against its counters.
• Thunder is like Stone Edge except with no STAB and a different effectiveness profile.

Smack Down is preferred for its high damage output backed by STAB, in addition to good coverage against common typings. Dragon Tail generally performs worse partly due to lack of STAB, though there may be niche cases where you'd want the Dragon-type damage and extra energy generation.

Meteor Beam is an incredible move - its superior DPE and guaranteed Attack boost is worth the slight cost increase over Stone Edge. Heavy Slam is Aggron's cheapest Charged Attack, although it doesn't provide much coverage and isn't exactly cheap or strong. Thunder is Aggron's strongest option against Steel- and Water-type targets, but a super effective Thunder is only 11% stronger than a neutral Meteor Beam. The addition of Rock Tomb following the GBL Season 10 update is unimpressive, as its poor damage output and high energy cost discourages its use despite its new debuff utility.