2 more defensive counters because I'm bored:
Counter:
Gourgeist-Super @ Leftovers
Ability: Frisk
EVs: 252 HP / 160 Def / 96 SpD
Impish Nature
- Will-O-Wisp
- Leech Seed
- Synthesis
- Foul Play
Gourgeist-Super easily takes hits from Landorus-T and has Recovery so it can't be worn down easily. Foul Play has a 75% chance to OHKO a +2 Lando-T after Stealth Rock, after his Stone Edge only did 55% max. Because of Frisk, Gourgeist-Super can also look at Lando-T's item. Foul Play is often the best play but if Frisk shows a Leftovers Lando-T at full health you could assume a more bulky SD set and click Wisp instead of Foul Play to win 100% of the time.
+2 252+ Atk Landorus-T Stone Edge vs. 252 HP / 160+ Def Gourgeist-Super: 174-205 (46.5 - 54.8%) -- 9% chance to 2HKO after Leftovers recovery
+2 0 Atk Gourgeist-Super Foul Play vs. 0 HP / 4 Def Landorus-T: 268-316 (84 - 99%) -- 75% chance to OHKO after Stealth Rock
Counter:
Tangrowth @ Leftovers
Ability: Regenerator
EVs: 248 HP / 228 Def / 32 SpD
Relaxed Nature
- Giga Drain
- Hidden Power [Ice]
- Knock Off
- Sleep Powder
Tangrowth is a really solid Landorus-T counter because it avoids the 2HKO from a +2 Stone Edge, so even if you miss Sleep Powder or HP Ice doesn't kill, you will still beat Landorus-T. Tangrowth also can't be worn down really easily because of Regenerator. HP Ice is the safest play because it will always 2HKO Lando-T, even if it runs Yache Berry, but Sleep Powder can be used so you have a big chance that you only have to take one Stone Edge before beating Landorus-T. Unfortunately you risk missing and Lando-T having a Lum Berry.
+2 252+ Atk Landorus-T Stone Edge vs. 248 HP / 228+ Def Tangrowth: 163-192 (40.4 - 47.6%) -- 3.9% chance to 2HKO after Stealth Rock and Leftovers recovery
0 SpA Tangrowth Hidden Power Ice vs. 0 HP / 0 SpD Landorus-T: 224-268 (70.2 - 84%) -- guaranteed 2HKO after Stealth Rock