Hard Counter: RestTalk Defensive Pivot Mega Garchomp
Now, Mega Garchomp is normally seen as a super-powerful wallbreaker (4 attacks set, can be mixed) or a sweeper (SD). This is a different beast, one that focuses on being a fat wall that hits harder than ScarfChomp with 0 attack investment that also shuffles things with Dragon Tail while being fatter than Standard TankChomp by a substantial margin.
I posted this set in Creative and Underrated Sets, and earlier in this thread (countering Magma Storm Heatran) where I show how this checks/counters a hell of a lot of meta Pokemon, and provides general team utility (plus a bunch more calcs), but let's get on to countering a true monster, Choice Band Tyranitar.
Garchomp-Mega (M) @ Garchompite
Ability: Rough Skin
EVs: 252 HP / 176 Def / 76 SpD / 4 Spe
Impish Nature
- Earthquake
- Dragon Tail
- Rest
- Sleep Talk
Defensively, versus CB Tyranitar
252+ Atk Choice Band Tyranitar Crunch vs. 252 HP / 176+ Def Mega Garchomp: 153-181 (36.4 - 43%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Choice Band Tyranitar Superpower vs. 252 HP / 176+ Def Mega Garchomp: 153-180 (36.4 - 42.8%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Choice Band Tyranitar Stone Edge vs. 252 HP / 176+ Def Mega Garchomp: 95-112 (22.6 - 26.6%) -- 97.6% chance to 4HKO after Stealth Rock
252+ Atk Choice Band Tyranitar Stone Edge vs. 252 HP / 176+ Def Mega Garchomp: 95-112 (22.6 - 26.6%) -- 30.6% chance to 4HKO
252+ Atk Choice Band Tyranitar Crunch vs. 252 HP / 176+ Def Mega Garchomp
on a critical hit: 229-271 (54.5 - 64.5%) -- guaranteed 2HKO
You eat up any of CB Tar's attacks; even if Crunch gets a crit as you switch in (assuming no Rocks for this), you have good odds to win the 1v1, because the second Crunch has roughly 50% chance to KO you. Stone Edge basically tickles you, as it doesn't even 4HKO most of the time (only with rocks is it guaranteed).
In comparison, Standard TankChomp gets 2HKO'd by Adamant Crunch after a very small amount of chip damage (Crunch does 42-50% to the standard set), and since you have no recovery, after one Stone Edge, Crunch 2HKO's standard TankChomp. You on the other hand, outspeed and can Rest up to full comfortably and Sleep Talk til you win, or just go for the EQ off the bat.
Offensively, versus CB Tyranitar
CB Tyranitar will generally either bring in Sand, or Sand will still be up when Chomp comes in. But let's assume worst-case scenario: sand isn't up.
0 Atk Mega Garchomp Earthquake vs. 72 HP / 4 Def Tyranitar: 314-372 (87.4 - 103.6%) -- 25% chance to OHKO
With pretty much any chip damage-1 layer of Spikes, or SR-it's over a 90% chance to OHKO CB Tar back.
0 Atk Sand Force Mega Garchomp Earthquake vs. 72 HP / 4 Def Tyranitar in Sand: 408-482 (113.6 - 134.2%) -- guaranteed OHKO
In sand, it's not even close.
But let's say you rested up, and Sleep Talk picks out Dragon Tail.
0 Atk Mega Garchomp Dragon Tail vs. 72 HP / 4 Def Tyranitar: 94-112 (26.1 - 31.1%) -- guaranteed 4HKO
Respectable damage, and your Dragon Tail does more damage than CB Tyranitar's Stone Edge.
AND REMEMBER, once you switch in, you force out CB Tyranitar and can fire off absurdly powerful Sand Force boosted Earthquakes (unlike many other counters which have comparatively weak EQs).
0 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Mew in Sand: 222-262 (54.9 - 64.8%) -- guaranteed 2HKO after sandstorm damage and Leftovers recovery
0 Atk Garchomp Earthquake vs. 252 HP / 0 Def Mew: 135-160 (33.4 - 39.6%) -- guaranteed 3HKO after sandstorm damage and Leftovers recovery
252+ Atk Garchomp Earthquake vs. 252 HP / 0 Def Mew: 180-213 (44.5 - 52.7%) -- 21.5% chance to 2HKO after sandstorm damage and Leftovers recovery
In conclusion, the ability to have something that easily can switch into CB Tar is hard to find, but combine that with something that has massive offensive power back and can shuffle while being tanky, and you've got something special in RestTalk Mega Garchomp.