Tornadus@Leftovers
Timid Nature, 252SpA/4SpD/252Spe
Hurricane
Rain Dance
Taunt
Focus Blast
Tornadus totally shuts Sableye down thanks to its faster priority Taunt. After Sableye is forced to attack with its laughable Night Shade, Tornadus can proceed to set up Rain Dance and thrash him with an STAB 120 BP Attack. Even if it switches in and gets burned by Will-O-Wisp, Tornadus will still win one on one, and be around for a few more turns to decimate with his fearsome attacks. .
Since Sableye and Tornadus are both things I've never really used that much, I decided to take a look at this out of interest. So let's take a look at how this plays out in what I view as Sableye's best case scenario:
Turn 1:
Tornadus (299 hp) switches in and takes 74 damage from stealth rock
Sableye (304 hp) uses Will-o-wisp, burning Tornadus
Tornadus takes burn damage (37 hp) and recovers with leftovers (18 hp) leaving it with 206 hp
Turn 2:
Tornadus uses Hurricane (I will assume it hits since it wouldn't be fair to do otherwise) and Sableye takes minimum damage (since it's a counter it should be able to win even with min damage rolls, also the max it can do is 79.3%), meaning that Sableye loses 204 hp and is now at 100 hp.
Sableye uses Night Shade meaning Tornadus loses 100 hp and is now at 106.
Tornadus takes burn damage and recovers with leftovers leaving it with 87 hp.
Sableye recovers with leftovers leaving it with 119 hp.
Now we reach an interesting situation, namely, since we're assuming min damage rolls, if Sableye recover spams Tornadus will need to attack three times to kill it meaning it will take three turns worth of burn damage and be left with 30 hp. However, if Tornadus taunts and Sableye night shades, Tornadus is dead.
Even if the Sableye user expects the Tornadus user to predict perfectly and acts to ensure Sableye lives the longest possible under those circumstances and even if the Tornadus user actually does predict perfectly, Tornadus is still going to need two more turns to kill Sableye (Taunt to stop Recover, Hurricane to kill), and is going to be left with 49 hp, a mere 16% of its health. At that point Tornadus is now unable to switch back in without dying, burned so it will only live three more turns max, and has no rain up meaning both its moves only have 70% accuracy.
I'm not entirely sure this makes Tornadus not a counter since Sableye is dead and Tornadus still has the ability to wreak havoc for a good three more turns, but I thought it was pretty interesting how much Sableye can cripple it before it goes down.