Pervisty Jaroda is very dangerous.If you lose your grass check, you are literally fucked. It's insane speed, an ability to simultaneously boost and attack at the same time make this thing a fearsome sweeper.
Speaking of that, Jaroda has very few true checks:
Partial Checks:
Nattorei - [strike]May as well not exist.[/strike] Resists HP Rock. Every HP Jaroda runs can hammer this thing's face in, and Natt can't do much but lay a layer of spikes during this. Can Natt even break Jaroda's subs?
Skarm - can assault with Brave Bird/Drill Peck and threaten to phaze with WW/Roar, but phazed by Dragon Tail, KO'd by Gemmed +4 HP Rock. If Jaroda's already pretty hurt and not well boosted, can kill it off.
Heatran - gives Jaroda a heart attack if it's not behind a sub, but badly damaged or KO'd by HP Ground if behind a sub. +4 Gemmed HP Rock hurts too after SR and a +2 Leaf Storm. Revenge killer.
Scizor - +2 Gemmed HP Rock hurts after SR and Leaf Storm. Revenge killer.
CB Bullet Punch hurts.
Shandera - scarf is its friend, but Substitute and Gemmed HP Rock are issues. Revenge killer.
Urugamosu - another one that needs scarf, but Sub and Gemmed HP Rock make it nonviable. Revenge killer.
Gengar - not too bad. Can easily score a scarfed revenge kill when Sub's down.
Grass types - Really, only
Celebi. Celebi can annoy a bit but Wring Out dominates it, HP keeps it picking recover, and Gem puts it within 2hko range with a few boosts. Jaroda can sub to avoid
Sleep Powder vs most grasses, though
Erufuun and
Mischievous Heart are problems if sub isn't up.
Jumpluff has no issues sleeping a Jaroda without HP Rock using
Slip Through.
Sceptile can be a solid counter when running X-Scissor.
Dragon/Flying types - Scarfed ones can revenge kill when Sub isn't up, but Gemmed HP Rock isn't something they want to tank, and Dragon Tail hits Super Effectively while getting them out of the field.
Crobat can survive a Leaf Storm or two, but +2 Gemmed HP Rock will take it down from behind a Sub.
Scarf Users in general are problematic to Jaroda, bypassing it's excellent speed and hitting it hard. Mostly revenge killers.
Weather Speeders are the same. Swift Swim, Chlorophyll, and Sand Throw are problematic, though only a few, if any, want to switch in on Jaroda behind a sub.
Yanmega and Ninjask resist Leaf Storm and Mega can Protect in order to put itself at the speed advantage. Yanmega has 2 reliable OHKOs and an offensive Jask can do great harm. Sub helps because Gemmed HP Rock ohkos.
True Checks:
Zeburaika - With Herbivore, can switch in on a Leaf Storm and outspeed to Overheat/Nitro Charge. Only risk: HP Ground
All other
Herbivore users -
Girafarig can't really do much but Double Hit or Psychic/Zen, but Jaroda hardly has any options either.
Mebukijika and Baffuron both have Megahorn and the attack stat to abuse it, and
Miltank has a decent attack stat.
Azumarill has Ice Beam, but Huge Power's a better trait. Most of these pokemon don't like Jaroda favorite HP Fighting, but meh.
Blaziken - Actually, not a true check that can wall Jaroda, but forces a KO war.
Switching in, if Jaroda doesn't have a sub, Ken wins.
If Jaroda does have a sub, and isn't boosted yet, Ken wins at 100% hp. At lower levels, Jaroda wins.
If Jaroda has a boost AND a sub, Ken's in deep trouble. But Ken shouldn't be coming in during such horrid circumstances anyway.