Landorus-Therian Duo Guide
Landorus-Therian is an absolute monster of a Pokemon. With a Base Attack of 289, which is higher than Rayquaza's, and the optimal Ground-type moveset in Mud Shot/Earth Power, Lando-T obliterates Groudon as the best Ground-type attacker. Landorus can also equip Rock Throw/Rock Slide and become the 3rd-best Rock-type attacker, despite lacking STAB. Yes, Landorus, despite not being a Rock-type, is a better Rock-type attacker than Tyranitar and Rhyperior, both of which are actual Rock-types.
The good news continues: Lando-T, much like Rayquaza, sports a 4x weakness to Ice and can therefore be duoed easily. Compared to its brother, Landorus-Incarnate, Lando-T is slightly squishier, which allows more Pokemon to be duo-viable. Absolutely duo as many Landoruses as you can if you care at all about strengthening your Ground- and Rock-type rosters, and if you want to maximize your Rare Candies from each Raid Pass.
- Rock Throw is not boosted by STAB; however, it has significantly higher Base Power and hits Ice-types for super effective damage, making it much more difficult to go against than Mud Shot.
- If you don't dodge, Focus Blast hits Ice-types extremely hard, and is the most difficult Charge Move to face. If you do dodge, Focus Blast is easier than Rock Slide to go against.
- Rock Slide is not boosted by STAB; however, it is super effective against Ice-types and can be used consecutively, making it quite difficult to face. However, Mamoswine's Ground typing means that Rock Slide is only neutral against it.
- Earth Power is boosted by STAB and has high Base Power; however, it does not hit any of the top Ice-types for super effective damage and is therefore easier than the above 2 Charge Moves.
- Outrage has high Base Power, but is not boosted by STAB and does not hit Ice-types for super effective damage, making it the easiest variant of Landorus to go against.
- Snow boosts the power of your Ice-type attacks, making the duo much easier. The solo is still impossible, even with Snow.
- Rain boosts the power of your Water-type attacks. Under Rain, Level 35 Swampert, Kingler, and Feraligatr become capable of duoing against all movesets; Level 35 Gyarados can duo against all movesets except Rock Throw/Outrage.
Viable Counters
Minimum viable levels assume Best Friends, no Weather, no Dodging.
Italics indicate a Legacy move.
Porygon-Z must have Hidden Power Ice to be duo-viable against Landorus. If it doesn't have HP Ice, it's not good enough, even at Level 40.
Against Outrage, Alolan Ninetales and Sandslash are duo-viable, thanks to their Fairy- and Steel-typings granting them resistances to Dragon. If for some reason you have a Level 40 Alolan Ninetales or Sandslash, feel free to use it against Outrage.
Earth Power is roughly the same difficulty as Outrage. If you have an Abomasnow at Level 40 for some reason, it manages to be duo-viable thanks to its Grass-typing granting it a resistance to Ground.
The difficulty of Rock Slide depends on what you're using. If you're using primarily Glaceon or Weavile, or other Ice-types, Rock Slide will be quite a bit more difficult than Earth Power or Outrage. If you're using primarily Mamoswine, Rock Slide will be easier than Earth Power to go against.
With no dodging, Focus Blast is much harder than the rest of Landorus' moves. However, Focus Blast is a 1-Bar move, meaning it comes out infrequently and predictably, and its damage window is very late, making it easy to dodge. Dodging Focus Blasts will significantly improve the performance of Mamoswine, Glaceon, and Weavile in this fight.