Physically defensive Arcanine is the best hard counter to this Scizor that I can think of. With this set up, Arcanine is only 4HKO after Stealth Rock, and he is also still a solid physical wall for many other pokemon (Anything that isn't Terrakion with Stone Edge, and anything that doesn't have a strong Earthquake or Stone Edge). His huge movepool gives him great coverage even with only three attacking moves, and with the high BP of his moves he still hits hard. He could also utilize Will-O-Wisp to cripple anything switching in when he forces something out. Morning Sun allows for reliable recovery, especially with sun support.
This is the set:
@ Leftovers
Ability: Intimidate
EV's: 252 Hp, 252 Defense, 4 Attack
Nature: Impish (+Defense, -SpA)
- Flare Blitz
- Extreme Speed
- Morning Sun
- Will-O-Wisp
This set makes him the most effective physical wall that he can be, and a very effective hard counter to this Scizor.
Some Damage Calcs For Scizor with zero boosts (at -1 from intimidate):
Scizor Superpower vs. this Arcanine: 20.8-24.73%
U-Turn does 9.11-10.93%
Bullet Punch does 9.37-11.19%
Pursuit does 10.41-12.5%
With a Swords Dance (at +1 from intimidate)
Superpower does 31.2-37.01%
That is the only relevant calc for this Scizor's set.
Damage Calc For Flare Blitz:
163.95-193.02%, Arcanine is faster than Scizor and will always OHKO.
As you can see, this Arcanine will be at best 3HKO by Scizor if he has a boost, and he will be a relevant counter or check for many other physical attackers in OU, despite being a UU pokemon.