I made a standard rain team once and honestly one of the simplest yet solid counter to it was Amoongus. Make a bulky one and spore the TR'r. Usually they don't run Chesto or Lum. Sometimes they will still get TR up but if you make Amoongus with min speed, he becomes one of the fastest mons and will spore whoever is a big threat.
Also don't run Superpower on Scizor, little to no need. Most common scizor sets:
Bullet Punch Bug Bite Acrobatics (Aerial Ace if no flight gem) Protect
Some take away Acrobatics and use Swords Dance.
Since you have a rain team you shouldn't need to worry about ohko'ing TTar as a bullet punch and any water move will take him out.
Also people will laugh at you for using a pure rain team but I've had tons of success using them, I had general teams as I never have a solid way of winning with them, 50/50 matches relying on BS hax and BS prediction hax.
Edit: Also for Credentials I've placed 5th in a regional last year and have place around top half in Nats twice in a row now. I'm not the greatest player by ANY means but I do play VGC extensively so I know the metagame pretty well.
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