i misread quagsire as quagmire, it was an honest mistake
anyways shantae should start with her hair whips? its her main thing. but they're not really at a melee range (nothing stated that they are so) so I think she'd probably start with magic instead.
Shantae's magic is kinda basic I'll add, but there's some solid stuff there like the shield that grants her invincibility. So that'll help her.
Bubble and Mirror also reflect and absorb projectiles, so, while temporary, would negate all of Wooper's projectiles.
Melee combat would also go to Shantae imo, stat amps, 4x AP difference naturally. And she can just turn into an elephant and ram into Wooper so uh
yeah going shantae for now
To Wooper's credit, Stat Amps are irrelevant due to Unaware.
As the profile rather strangely puts it:
- Unaware: When Quagsire is hit or hits, the statistics boosts of the opponent matters naught.
Strange in part because Wooper can have this Ability, too, yet they write it as if for Quagsire.
As Bulbapedia more technically puts it:
"If a Pokémon with this Ability uses a damaging move or is targeted by a damaging move, the other Pokémon's stat stages are ignored during damage and accuracy calculation.
Specifically, when a Pokémon with this Ability uses a damaging move, the evasion stat stages of the targets are ignored during accuracy calculation, and the Defense and Special Defense stat stages of the targets are ignored during damage calculation; when a Pokémon with this Ability is targeted by a damaging move, the accuracy stat stages of the attacking Pokémon are ignored during accuracy calculation, and the Attack and Special Attack stat stages of the attacking Pokémon are ignored during damage calculation."
Shantae would be wasting time if she stat amped herself, & giving Wooper at least 1 window of opportunity, & given she probably doesn't know about Wooper's ability, she won't know she's wasting time.
But when Shantae is over 3.75x stronger to begin with, & Wooper seems kind of passive, those opportunities might not matter much.
The best things Wooper could do are:
A. Shantae hits it physically, Wooper uses Counter to deal double the damage it took. However, considering Shantae has more Durability, she might handle this well. The Stamina matchup is unclear since Shantae lacks a justification. This is unlikely though, because a more technical, martial arts-like move like Counter that's an Egg Move seems OoC for Wooper.
B. Toxic. This inflicts Bad Poison, a distinct status from regular poison. In gameplay, regular Poison does 12.5% (Or one 8th) per turn, while Bad Poison starts at 6.25% (Or one 16th) per turn, & increases by another 16th every turn. (For both kinds of Poison, rounding down.)
So: Turn 1: 6% Turn 2: 12% Turn 3: 18% Turn 4: 24% Turn 5: 30% Turn 6: 36%, & so on & so forth....
Arguably, this could just be an unquantifiable increase in Poison severity every time it inflicts harm, assuming we ignore the game's numbers as metrics. In gameplay, this means that because 6+12+18+24+30+36=126, which is more than 100, Toxic KOs after just 6 instances of Bad Poison incrementation damage. One could stave it off with healing, but the damage increases.
Although, even then, Toxic working out requires assuming Wooper will try it -It does put a toxic film over its body on land, so this is semi-plausible- AND can survive long enough that about six incrementations of Bad Poison happen.
C. Yawn. In gameplay, 1 turn after the user uses this, the target falls asleep. This'd put Shantae on a clock to beat Wooper before she gets incapacitated, assuming she sleeps long enough or Wooper can beat a sleeping Shantae. Since it's just Wooper Yawning, it's kind of hard to avoid, too.
In theory, there's other stuff like Acid Spray, but that's dodgeable, kinda OoC (Wooper might not spray acid since it's not a Poison-type, & its film is also to keep it from dehydrating on land.) Stockpile (OoC), Amnesia (Doesn't counter Physicals.), or Recover, which might let it survive Shantae attacking, but only works out if she exhausts herself trying, since the AP gap means Wooper might not survive to do enough other than Recover if it can't find a way to avoid getting attacked again each time it heals.
(Toxic+Recover MIGHT work, I guess...?)