Upon its release in BW, Terrakion immediately became a defining force of the metagame, with a variety of powerful sets that were all good options and could destroy unprepared teams. With an immense base Attack stat of 129, coupled with its Rock / Fighting typing giving it near-perfect coverage with only its STAB moves and essentially giving it two free moveslots, and a wonderful Speed tier of base 108 to outspeed the majority of the metagame, Terrakion quickly gained a deserved reputation for being one of the best Pokemon in OU, as well as the notorious status of being arguably the hardest Pokemon to safely switch into. In addition to purely offensive sets, it also had an effective Focus Sash lead set that could get Stealth Rock up quite easily.

The transition to XY did not do Terrakion many favors, though, with many Mega Evolutions being able to beat it one-on-one and the addition of Fairy types hurting it as well. But it was in ORAS that Terrakion finally dropped from OU to the BL tier, banned almost instantly by the UU council. This was the metagame shift that favored Terrakion least, bringing the metagame's most important Speed tier from base 100, with Mega Charizard X and Y and Mega Gardevoir, to 110, which became quite crowded with the addition of Mega Metagross, Mega Gallade, Mega Diancie, and the Mega Lati twins, as well as introducing a few defensive Mega Evolutions that can switch in on Terrakion in the form of Mega Sableye, Mega Slowbro, and Mega Altaria. Arguably its best set in XY, the Focus Sash + Stealth Rock lead set, gets almost completely shut down by Mega Sableye, and the other changes to the metagame resulted in it dropping down to UU's banlist. Despite all of the disadvantageous changes to the metagame that ORAS brought, though, Terrakion remains an incredibly potent offensive Pokemon.

Terrakion @ Life Orb
Ability: Justified
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Close Combat
- Stone Edge
- Swords Dance
- Substitute

If you can get Stealth Rock on the field and can find a free turn of setup with this monster, very few Pokemon can take its attacks. Slowbro and its Mega Evolution are the only two OU Pokemon that can definitely take a +2 Stone Edge after Stealth Rock damage and can also chew a +2 Close Combat. Even Mew has a chance to be OHKOed after taking Stealth Rock damage! With the astounding coverage gifted to it by its two STAB moves, the two other moves on this set are used to make Terrakion an unbelievable wallbreaker. With a +2 Stone Edge or a +2 Close Combat OHKOing almost all of the fatter parts of the metagame, the remaining few will find themselves very upset when they attempt to burn or paralyze Terrakion only to find it sitting behind a Substitute, safe from the effects of their status moves.

Unfortunately, this set leaves Terrakion at the mercy of the faster metagame, most of which has little trouble dealing with the legendary bison. The entire list of newly introduced Mega Evolutions in the base 110 Speed tier mentioned earlier all OHKO it with their STAB moves, Alakazam and the Lati twins have no real trouble dispatching it, Tornadus-T will frequently run Fighting-type coverage to hurt Terrakion, Thundurus's Prankster Thunder Wave cripples it and any Fighting or Grass coverage outright OHKOes it, Mega Lopunny destroys it, and so on. As would be expected from a powerhouse like Terrakion, though, it has no real trouble adapting to this, as it can also run a devastating Choice Scarf set that outspeeds and OHKOes almost everything faster, although this does sacrifice some of its potency against bulkier builds. Terrakion has the power to obliterate balance and the Speed necessary to make a Choice Scarf set the bane of offensive teams at the same time, so if you feel like supporting it with the rest of your team by bringing a good Psychic- and Water-type switch-in, Terrakion is an excellent choice for a teamslot and should manage to achieve something in almost all battles.