Hm, didn't think I'll lose so early, but o well, I just got 192 streak on Double Battle Hall today with this team:
Metagross Level 50 @ Focus Sash
Adamant
IVs: 22 / 31 / 31 / x / 27 / 27
EVs:152 HP 252 Attack 4 SpDef 100 Speed
(Basically enough speed to outspeed neutral base 80s with no speed EVs)
- Protect (Pursuit) / Bullet Punch / Thunderpunch / Ice Punch
Metagross Level 50 @ Choice Scarf
Adamant
IVs: 31 / 31 / 24 / x / 21 / 31
EVs: 4 HP 252 Attack 252 Speed
- Explosion / Iron Head / Thunderpunch / Earthquake
Basic Strategy: Should be pretty much self-explanatory. Protect + Explode on most things. Thunderpunch on both sets are for damp pokemon. Iron Head for STAB and accuracy, Earthquake for Steels. Bullet Punch for sashers. Ice Punch is for additional coverage (which I now think might be be better replaced with something else because of how I lost). I had Pursuit in my first 20 streaks where I battled bug and ghost, in case I see Shedinja (which I did).
Oh yeah, I don't usually explode when facing pokemon holding lax incense / Bright Powder (... and quick claw sometimes if my other moves will 2HKO anyway). I don't explode on most Rocks or Steels, and obviously not ghosts.
Biggest Threats that only appear before 170 streak:
Shedinja (already mentioned... Pursuit takes care of that)
H203 | Quagsire | Modest | Mystic Water | Earth Power | Muddy Water | Yawn | Endure | Def/SpA
--> It's good that this thing doesn't appear in Rank 10, so I won't have to have moves to deal with it specifically.
The other big threats:
H444 | Infernape | Adamant | Life Orb | Close Combat | Flare Blitz | Mach Punch | Fake Out | Atk/Spd
H460 | Magmortar | Mild | Lax Incense | Fire Blast | Hyper Beam | SmokeScreen | Protect | Spd/SpA
H474 | Heatran | Modest | Focus Band | Magma Storm | Flash Cannon | Lava Plume | Metal Sound | SpA/SpD
H421 | Entei | Rash | Quick Claw | Eruption | Rock Climb | Flamethrower | Fire Fang | Spd/SpA
--> I didn't encounter any of these fire types. Sash Charizard will also win if Blast Burn burns me.
H373 | Rotom | Timid | Petaya Berry | Shadow Ball | Thunderbolt | Signal Beam | Swift | Spd/SpA
--> This is one of the reasons why I had Ice Punch. Iron Head does minimum 38%. Ice Punch does minimum 48%, so Iron Head + Ice Punch + Bullet Punch is guaranteed KO. I figured this is what happens: 1st Turn: Iron Head + Ice Punch on one Rotom. Rotom's Thunderbolt doesn't 2HKO, so 2nd Turn: Bullet punch finishes one Rotom while Iron Head does 38% to 2nd Rotom while the 2nd Rotom finishes one of my Metagrosses while the other is still at full health to take on the 62% health Rotom for 2HKO (with 2 Iron heads or with Ice Punch + Bullet Punch) while taking only 1 hit. Without Ice Punch I lose to Rotom for sure.
Well... this was how I lost, against Rotoms lol.
Turn 1:
ScarfGross used Ironhead on Rotom 1 (~40% damage)
Rotom 1 used Thunderbolt on ScarfGross. ScarfGross is paralyzed.
Rotom 2 used Thunderbolt on ScarfGross. ScarfGross has ~7% health left.
SashGross used Ice Punch on Rotom 1. Rotom's Petaya activates.
Turn 2:
SashGross used Bullet Punch on Rotom 1. Rotom 1 faints.
Rotom 2 used Thunderbolt on ScarfGross. ScarfGross faints.
Turn 3:
Rotom 2 used Thunderbolt. It's a Critical hit! SashGross has about 10% health left.
SashGross used Ice Punch which did about 50%.
Turn 4:
SashGross used Bullet Punch which doesn't KO.
Rotom KOs with Thunderbolt.
So, without the critical hit OR the paralysis, I could have won, but o well.
I'm thinking I should really just use another item instead of focus sash, because so far, the focus sash has activated a total of 0 times... ...
EDIT: I kind of want to start another streak using metagross again, but ugh, Battle Hall is just too boring using the same 1 pokemon so many battles.