At that moment, I had the following: Yanma on the field at 1%, modest, with Protect, Air Slash, and Bug Buzz, Fletchling at full, no item, acrobatics, and Tangela at about 50% (it didn't matter). Expulso had a presumably eviolite Mienfoo at about 56% before regenerator, with fake out and some other moves, along with a Tangela on the field that had just taken stealth rock damage. Stealth rocks were up on his side, and there was no weather.
Unless Expulso was running some specially bulky tangela (which I have no way of knowing), Bug Buzz would OHKO. Mienfoo could then come in, attempt to fake out (which would be blocked with protect) and then air slash would either a) KO or b) put it low enough that Fletchling would easily KO with air slash.
However, even if Tangela had survived, and proceeded to giga drain, it would have been left low enough that Fletchling could take it out with acrobatics. That begins to make things murkier, however I would still win.
The only mienfoo set that can survive Fletchling's acrobatics is a 236/196, as Mienfoo would have been around 79 or so percent after rock damage. However, the chance of surviving would have been absurdly low.
196+ Atk Fletchling Acrobatics (110 BP) vs. 236 HP / 196 Def Eviolite Mienfoo: 18-24 (75 - 100%) -- 6.3% chance to OHKO after Stealth Rock
The first, and fairly obvious move, is to fake out fletchling. That does a decent chunk to fletchling's HP.
76+ Atk Mienfoo Fake Out vs. 0 HP / 92 Def Fletchling: 5-6 (23.8 - 28.5%) -- 22.8% chance to 4HKO
At this point, Fletchling is at (assuming the worst case scenario for me) 16 HP (21-5). A drain punch after surviving the acrobatics at 1 HP has a 6.3% chance to do 15 damage, which would finish Fletchling off if Fake Out did 6 damage. That's not the worst case scenario for me, however, if it was a crit, it would put Expulso in a better position.
76+ Atk Mienfoo Drain Punch vs. 0 HP / 92 Def Fletchling on a critical hit: 18-22 (85.7 - 104.7%) -- 43.8% chance to OHKO
At this point, Mienfoo would have 9 HP (1+8 from a drain punch taking off 16 HP). However, my Tangela at 15 speed would go before Mienfoo and finish things.
200+ SpA Tangela Giga Drain vs. 236 HP / 0 SpD Eviolite Mienfoo: 10-13 (41.6 - 54.1%) -- 56.3% chance to 2HKO
Of course, the absolute worst case for me would be if Expulso drain punched right off the bat, got a crit, and killed Fletchling. This would put Mienfoo at 11 HP instead of 9, so it could possibly take a giga drain from Tangela. This does not change the result.
76+ Atk Mienfoo U-turn vs. 0 HP / 0 Def Eviolite Tangela on a critical hit: 10-14 (43.4 - 60.8%) -- 88.7% chance to 2HKO
This is Mienfoo's best shot, as it cannot recover enough HP from a critical drain punch to survive another giga drain. At this point, my Tangela (at around 11 HP at the beginning of all of this) might have been in trouble, if it weren't for Giga Drain. Tangela then sits at a comfortable 16 HP, enough to take the U-turn, and end it with Giga Drain. I can say, with virtually no doubt, that I had won this match beyond the realm of hax.