Butterfree's main downfalls were...pretty much everything really. Its highest stat was its base 90 SpA which just isn't offensive enough anymore with the power creep. It lacked bulk, especially on the physical side. Base 70 Spe is a very awkward speed tier, easily outsped by most threatening opponents. Bug/Flying is a horrid defensive typing and underwhelming offensive typing. All it really had going for it was Quiver Dance and Compoundeyes Sleep Powder. This optimized Butterfree has much better stats all around, as well as a better offensive typing that isn't 4x weak to Stealth Rock and a signature move that gives it greater offensive presence. Compoundeyes Sleep Powder still has its niche but Magic Guard allows Butterfree to avoid hazard and status damage, which could otherwise wear it down quickly.
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Beedrill [Optimized]
Abilities: Intimidate /
Skill Link (HA)
Stats: 75 HP / 120 Atk / 70 Def / 45 SpA / 90 SpD / 125 Spe | BST: 520
Added Moves: Stinger Storm*
Summary of Changes: +10 HP, +30 Atk, +30 Def, +10 SpD, +50 Spe
*Stinger Storm:
| 25 BP | 95% Acc | 15 PP |
| Z-move: 140 BP Acid Downpour | Hits 2-5 times, each hit has a 10% chance to poison
Beedrill was even more frail than Butterfree and other Bug-types, leaving it unable to switch in and set up. Base 75 Spe and base 90 Atk were too low to be immediately threatening. Its abilities were also generally useless, relying on having low health or on luck. Optimized Beedrill has much greater offensive presence, with higher attack and speed, useful abilities, and a new signature move. Skill Link allows its STAB moves Pin Missile and Stinger Storm to hit five times each to break through Substitutes, Focus Sashes, and Sturdy. It now can more easily threaten switches to set up with Swords Dance, or it can U-turn quickly to a teammate.
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Beautifly [Optimized]
Abilities: Tinted Lens /
Triage (HA)
Stats: 90 HP / 110 Atk / 80 Def / 70 SpA / 90 SpD / 80 Spe | BST: 520
Added Moves: Dazzling Gleam, Moonblast, Play Rough, Draining Kiss, Leech Life, Beauty Kiss*
Summary of Changes: +30 HP, +40 Atk, +30 Def, -30 SpA, +40 SpD, +15 Spe
*Beauty Kiss:
| 75 BP | 100% Acc | 10 PP |
| Z-move: 140 BP Twinkle Tackle | User recovers 75% of the damage taken by the target, heals the user's status
Beautifly suffered from a combination of poor bulk, low speed, and being outcompeted by other Bug-types that left it practically useless. Optimized Beautifly has much better stats, a useful ability in Triage that goes well with its new signature move, and a partial Fairy typing for better offensive coverage. Triage gives +3 priority to its main STAB moves in Leech Life and Beauty Kiss, which allow it to hit fast and decently hard off its base 110 Atk stat while providing some recovery for better longevity. It has greater bulk and a better typing to help take advantage of this too.
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Dustox [Optimized]
Abilities: Corrosion /
Regenerator (HA)
Stats: 100 HP / 50 Atk / 100 Def / 85 SpA / 120 SpD / 65 Spe | BST: 520
Added Moves: Clear Smog, Toxic Thread, Toxic Spikes, Venom Drench, Thunder Wave, Toxic Gust*
Summary of Changes: +40 HP, +30 Def, +35 SpA, +30 SpD
*Toxic Gust:
| 80 BP | 100% Acc | 10 PP |
| Z-move: 160 BP Acid Downpour | 50% chance to badly poison targets, can hit and poison Poison-types and Steel-types
Dustox was similarly useless like its evo-cousin Beautifly but was also extremely passive. The optimized Dustox has hugely improved bulk with access to Regenerator so it can be a slow bulky pivot for its team with U-turn. While its special attack is still lacking offensively, it gets Corrosion to spread poison to opposing Poison-types and Steel-types that would otherwise switch in freely, along with Toxic Spikes to further support its team. Its signature move Toxic Gust provides an offensive way to spread badly poisoned status without fearing Taunt, as well as being able to hit Steel-types.