Most defensive Steel-types are good counters to Scizor as long as they don't switch into a super effective Superpower or Brick Break. Skarmory is probably the best initial switch-in, as it is easily able to take any of Scizor's attacks and set up hazards. Furthermore, if Scizor acquires too many boosts, Skarmory can just phaze it away with Whirlwind. Heatran boasts the signature distinction of 4× resisting both of Scizor's STAB moves, while also being faster and threatening an easy OHKO with any Fire-type move. Bulky Water-types such as Jellicent and Rotom-W can safely wall Scizor, and can even cripple it with Will-O-Wisp. However, they must not become complacent, as Scizor may break through after garnering enough Swords Dance boosts. Rotom-W often carries Hidden Power Fire to surprise Ferrothorn, and can OHKO Scizor while laughing at Bullet Punch, which it doubly resists. Gyarados resists Bug-, Steel-, and Fighting-type attacks—in other words, the entirety of Scizor's offense—and can further reduce Scizor's Attack with Intimidate, batter Scizor with its powerful STAB Waterfall, or phaze it with Dragon Tail or Roar. While it has fallen from popularity in BW, Zapdos also resists Bug-, Steel-, and Fighting-type attacks, and can destroy Scizor with Heat Wave or STAB Thunderbolt. Many fast and powerful sweepers can shrug off a Bullet Punch and successfully revenge kill Scizor; this list includes but isn't limited to Infernape, Hidden Power Fire Starmie, and Victini.
Jellicent is probably the best Scizor counter there is. It resists its STAB moves, isn't affected by Superpower, and can Will-O-Wisp Scizor, instantly crippling it. Take note though that Scizor is sometimes paired with a Pokemon that knows Volt Switch, usually Rotom-W. Should Scizor U-turn out on Jellicent, the corresponding Volt Switch Pokemon can come in and hit Jellicent hard. The same applies to the allergic-to-electricity
Skarmory, who takes all of Scizor's moves well and can set up hazards or Whirlwind out Scizor should it gain a boost. Gyarados, with Intimidate and its typing, is also in the same boat. Should the rain be up, Tentacruel also makes an excellent counter to Scizor since it takes low damage from its STAB moves and heals back the HP lost that same turn. It can retaliate with Scald, hoping for the burn on Scizor. Gliscor is also a pretty good option for dealing with Scizor, just watch out for Swords Dancing Life Orb versions—they'll deal with Gliscor easily.
Fire-types often cause Scizor to be clinically depressed as they easily kill Scizor.
Heatran kicks things off by outspeeding and KOing Scizor with whatever Fire move you have on it; all Heatran fears is Scizor's Superpower, which it doesn't usually spam as many Pokemon in OU can set up on it.
Volcarona can set up freely on any of Scizor's moves and cause trouble for the rest of the team. Infernape isn't bad either, but since it is more frail than a breadstick, it can't really switch in on Scizor's moves without taking a big chunk of damage. Magnezone, whilst it can't come in on Superpower, can trap Scizor and defeat it with Hidden Power Fire. If the opponent sees Magnezone in Team Preview though, they'll probably be U-turning like crazy, meaning Magnezone can only really trap Scizor after it's killed something with Bullet Punch or Pursuit. Rotom-W rounds this analysis off by outspeeding Scizor and either hitting it hard with any of its STAB moves or Hidden Power Fire, or crippling it with Will-O-Wisp. Even if Scizor is at +2 Attack, Bullet Punch will do little to Rotom-W. However, unless Rotom-W is physically bulky, a Choice Band U-turn from Scizor will hurt a lot.
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