Can [insert pokemon here] beat USM w/o affliction? (water starter edition part 1)

 

The rules as always:
- this is about seeing the availability, so starting at lvl 100, and the levelupmoves are manualy updated if needed
- starting from the pokecenter at the pokeschool
- starting with the level 5 moveset, unless the pokemon don't have 5 moves at that level, or is island-scan pokemon
- starting at the lowest form you can catch the pokemon in-game
- island-scan pokemons can not have hidden ability
- trade evolutions and version exclusives don't run
- everyone gets maxed out friendship for convenience sake (only effects the use of Return)

Feebas:
starting moveset: tackle, splash, flail
First 4th move you can learn is Round. Remember, you cann ot learn Beach-moves as 4th move until you get it from levelup or TM!
Also, as all moves at the start are Normal, have to avoid NPCs with ghosts (technicaly you can win against them by Strougle, but that takes ages).
At the Beach I quickly learn Water Pulse and Iron Tail just for variety.
Guzma in Po Town was extremly hard, the key with physical build is Iron Tail. Should try Icy Wind too (not good unless you fish for a freeze). Oh, and first turn Protect.
After that adventure finaly coulod swap Tackle to Return.
Final Guzma was delt with Flail (held item: metronome - as always).
Aaand there is no way to pass the Dragon Trial.

Clamperl:
starting moveset: Clamp, Iron Defense, Water Gun -> Water Pulse, Whirlpool
At the first of the Dragon Gauntlet has a water-immun Lapras, so get another move. You don't have much choice, so it's either Round, Return, or Icy Wind.
CAN beat UN with Epert Belt, Shell Smash, Icy Wind.
Ghost Room: Shell Smash (1), Water Pulse
Bird Room: Icy Wind
Rock Room: Water Pulse
Molayne kills the run. Theoreticaly you could hope the Megnazone casts Screech instead of Thunderbolt, and go from there, but I don't have that kind of patience.

Onix:
starting moveset: Rage, Rock Tomb, Rock Throw, Rototiller (this move is useless)
Buy Bulldoze and get rid of Rototiller, and on Island3 I learnt Iron Head, just for variety. OH was actualy need for flinching Faba's Claydoll.
For Dragon Trial pick up Dragon Tail.
UN: Bulldoze -> Dragon Tail Z. You need one of them being a crit.
I should have failed at Hapu, but I got a zounds of flinches on herwith Rosk Slide, which all connected, so passed this time.
Ghost Room: Brutal Swing
Bird Room: Rock Slide
Rock Room: Bulldoze
Molayne: Double Team -> Bulldoze (DT required, because the Magnezone will oneshot you otherwise)
Hau: Rock Slide

Zorua:
This pokemon is a "weird one", as its pre-evolve form is a physical-attacker, while its final form is special. And they have move-variety differences. I'll do my best to give the best chance to Zorua first.
starting moveset: Leer, Scratch, Pursuit, Fake Tears
You have options for your Dark move, pick your poison, and pick up Thief just in case. Aerial Ace, U-Turn and Return will also serve. I put my trust into at evolution upping the stat would compensate for the change in moveset - and in the meanwhile I'm avoiding using the type of moves that don't have alternative in special.
Against Guzma final you'll need Protect.
At Lusamine roll until she starts with Hypervoice, not the other two possible moves, or you'll run out of HP. Not sure what an Special build would use here, I used Aerial Ace. You might try Bounce.
Against UN used crit U-turn Z.
Ilima forced me to evolve.
Ghost Room: thief
Bird Room: Return
Olivia: Low Sweep
Molayne: Low Sweep (no idea why the Klefki never tried to paralyze me)
Hau: ... Now this is complicated. Thief the Raichu, Low Sweep the Tauros, Incineroar and Craboniable where you either have to crit the Inci, or the very least it should only drop a Flare Blitz not a Z (I guess you have a 50% chance). Then U-turn crit the Leafeon if you did not crit before, because it has Quick Attack. THEN you switch to Thief/Night Slash again to pick off the Noivern. I'm not doing the statistics how lucky you have to be for this.

Pyukumuku:
starting moveset (I've breeded one, so this is not just guessing): Bide, Helping Hand, Mud Sport, Harden.
As this one does not have direct attackm oves, just damage-reflection, I put EV into HP instead of Speed.
I got bored by just having Bide, so added Counter and Taunt. This run will take a while...
There is this video on youtube with solo pyku run https://www.youtube.com/watch?v=k1w2dZhEfA8 but does not tell wether afection was used or not, and eitherway missing key informations, and uses illegal moves at times (eg. has swagger at Hapu). Also, started against thw "wrong" starter (Hau has the water starter, not the fire one). Like when you come out from the cave with Albino Girl's pokemon, you DESPERATELY NEED Safeguard. Everything is ranged so Counter barely worth anything, they paralyze and confuse you. All of 'em. Unless you don't mind loosing. Tbh, I'm considering lowering my level to receive more damage. Not sure how Bide actualy works you know.
Against Mr. Chief you want to Bide-Z the Makuhita. The others don't ruin your stats, it does.
I'd also suggest attempting this buy a lot of health-potions, so you can Struggle. That is reliable, and much more convenient most of the times. Unfortunately because of the recoil even under the best of circumstances you can only knock down 3 enemy-pokemons before healing. Berries would help here a bit, but planting and witing for them don't even come to play until halfway the 2nd island :(
After fightinh Poipole the first time you can pick up Sleep Talk. I don't expect to use it, but just in case, I mention it.
When reaching the Marowak Totem you'll need to grind up to learn Toxic, there is no other way. Along this might wirth mentioning you can buy Protect and Safeguard as TMs. And you "most probably" want to keep Recover from the learnset. So this is a very inconvenient stage of the challenge.
You know what, let's go through the moveset: you want NOTHING from the Beaches, but just in case these moves are relearnable from there: Gastro Acid, Pain Split. Recycle might be useful if you can add to your movelist, and are using berries.
From the levelup-learnest these moves are entirely useless: Baton Pass, Water Sport, Helping Hand, Soak, Memento.
And these TMs are post-game: Quash, Substitute
Also, don't forget you have Z-crystals, so use them to shot down/damage hard the Salazzle.
At the Caravan-park we get Taunt as TM. That MIGHT come in handy, so grab it.
For the Ghost Trial you have to go in WITHOUT MOVES. Ghastly&Co are immun to everything you have. Aside struggle. So bring with you all kinds of medicines: healing potions, paralyze heal. For me it was possible to win with Sturggle, holding a Figgy-berry. Had 24 HP left, but you can have the luck that Banette misses with Will-o-Wisp, Struggle knocks down Banette (you have no control who it aims at), and so on. You on the other hand might want a PP-berry to be eaten before the battle, or an elixir, or something like that and use Toxic, and/or whatever. Banette is a hugh problem, as it can Curse, and remember, you have to arrive Mimikyu's closet with 0 PP because of the ghastly-line. So maybe you need Recover-PP too. I'm just theorising with this one of course.
In Po Town beware NPCs with haunters and such, and pokemon with no damaging moves (I know a salandit which comes second, and only does toxic and something other non-damaging - had to reload). The guy on the road is one with a Haunter, so always climb the hill to get to the town.
Back in the Aether Foundation you finaly get Toxic as TM, so you get at least minimal flexibility in your movepool in case you want/need that.
At Lusamine you should hope the Cle... won't lower your special defence much, then the 2nd will be that grass-thing, which'll hurt you a lot. You probably want to use your Z-move on that one.
At the dragons' Den the 2nd NPC worth mentioning, you want to Z the eagle, as it will otherwise Will-o-Whisp you, what is not good. And the 3rd has a Gengar, fortunately only sends it oout last. I suggest burn your PPs, especialy Bide on Route 1 before doing him.
The Grass Trial during the Gauntlet Run is EXTREMLY hard, you'll need Toxic, Recover and Safeguard there, bloody good timing your moves, and a hugh amount of luck. And for those in the back seats, yes, you have to delete either Bide or Counter here, which you won't get back until you reach The League!
Sophocles is another though cookie. Two of his mons are Steel-type, meaning immun to Toxic, and Togedemaru will hurt you when you knock it down. Worse, Magnezone has special moves only. This means if you do not have Bide, I have no idea how you'd defeat this team. Also becuase the Magnezone hits you super-effective and it shows, and the Golem will Z-move you, I even suggest to have a Figy-berry or similar as held-item, which will fully heal you with a Recover in the same turn.
After you get to the Gate of The Leage teleport back to Island 1 to grab Swagger. Just to be sure.
If you go to grab the Max Elixir behind Worker Ovid on Mount Lanakila (first cave-part when you go from below, lots of pushable blocks), do not waste your Toxic on the Relicanth. I mean it has 7, maybe 8 dose of Rest on it, which'll null any damage you caused to it, so don't try to poison it while it is asleep, and use any other move when it is, and even use Bide to lower its HP to make it use Rest without it being poisoned! It takes a ton of time, but now you know. 
I suggest you re-learn Counter at the Move Reminder.
Bird Room: Toxic, Recover, Counter, Bide.
Olivia: because we'll have PP-issues, come here second. We DO have enough PP to win this part, but MaxPP Recover, and preserve Bide against the Cradily and especialy the Probopass what is partialy Steel, so Toxic won't work oon it. On Armaldo Counter works wonders. Because of the low hit-chance of the Rock-type moves, and the paralyzis you'll suffer, there is a lot of factor here, and Olivia has 2 Full Restor, and 1 Full Heal to get rid of poison. Btw, Probopass will ALWAYS set up Sandstrom first, so bide that turn with something. No, I don't mean use Bide, on the contrary. More like throw a useless charge of Toxic at it, or use the time to Recover. The time Sandstorm will die out Probopass will sue ThunderWave here. You want to deal with the chances though, as removing a move for Safeguard sounds like a BAD idea.
Ghost Room: Consume a Max Elixir (that reset all moves PP, right?). You'll need Toxic to deal damage, Recover to heal, and a bunch of other PP to spend your turns with whole Toxic eats the ghosts away. Held item should be a healing berry.
Molayne: I had 3 Max Elixir originaly, so PP was not that much of a problem, but dealing damage here is not easy. Especialy considering Klefki. Your only chance there is Swagger. And to outlast the potential damage, you'll need Double Team. And you obviously can't give up Recover. Now the real question is, wether to preserve Bide or Counter. And while I'd prefer Counter, that's worthless against special attackers :(
You have 2 path to pass this room. One is to have Bide (Max PP preferred on it), Swagger (mainly to damage Klefki), Double Team to stall, Recover to stall evenm ore. Magnezone is always a problem as it is special attacker, so with all the defense-lowering the team throws at you, might off you anyway. You WILL run out of PP, but I did want that at the end to off Magnezone which somehow remaind for last.
The other option is to leave Counter on, and use that against everything but the Magnezone and the Klefki. Use Bide to defeat the Magnezone.
Both option is highly unreliable, will take a ton of tries (for my first win I set here 2 hours with 10 times spee), but it is not impossible.
Oh, and you better have a HP-restoring berry in hand. Just like for Hau. Well, you do have other option actualy...
Don't forget to refill your PP for Hau along the usual HP-healing! I've consumed 2 Max Elixir and 2 Elixir during The League (aka. 3 times refilling all PP from zero to max), and Bide and Recover got MaxPP-ed.
Hau can't really do much after you deal with the Raichu. I was out of HP-berries (I was lucky to have 3 to be honest, which neither threatened to confuse me), so I checked my inventory, and found one that resisted supereffective electric moves. I thought why not try it, and it worked out, Raichu went down first turn. Leafeon comes out, but it's no biggy actualy. If you don't have your HP too low, it'll be fine, ESPECIALY if you did not give up Counter for Double Team. Most of Hau's remaining pokemon are physical, so they don't really bother, though there is a Dizzy Punch in the reperoir, but it tends not to be a bother. But pay attention to have enough BidePP left for the last-coming Noivern, which is special-attacker. Would be awkward to fail just because of this factor.