DarthMagikarp85, take an Oddish, preferably female, and name it Lucy. Lucy has had a really hard life due to the fearsome bikers that terrorize it on Route 110, and so it is rather bitter and angry. It must learn Acid or Acid Spray ASAP and never forget it, since it is so angry and acidic. It must solo every single trainer on Route 110 bar yellow mons due to its anger, excluding wild Pokémon. It must also solo two trainers in Wattson's gym, since bikers like Electric-types and Wattson uses them. These solos have higher priority over Rufus's.
After it accomplishes these objectives, it realizes it has considerable power and dreams of what it could accomplish with it. Solo Tabitha to show weaknesses don't matter, and evolve into Gloom.
As Gloom, you want to spread poison everywhere, but also feel niceness tugging from your Grass-type side. Flip a coin to decide your path. If heads, solo all Grass-types to remove your weakness, and if tails, solo all Poison-types to remove this evil corruption. Do not evolve until you beat Norman (not a solo). If heads, evolve into Vileplume and if tails, evolve into Bellossom. Either way, remove the solo restriction.
As a Vileplume, learn Poison Powder or Toxic and poison everything you face bar Poisons and Steels to kill nature in your demented hatred. As a Bellossom, instead use Sleep Powder on everything you face to give it a gentle end.
To recap:
Oddish named Lucy.
Solo everyone on Route 110, except wild mons and mons Rufus has to solo.
Solo two Mauville Gym trainers.
Solo first Tabitha fight to evolve.
Flip a coin, heads is Vileplume, tails is Bellossom. Do not evolve until Norman.
Solo all Grass-types if heads and all Poison-types if Tails until Norman.
If Vileplume, spread Poison. If Bellossom, spread Sleep.