Ledyba is... weird. There isn't really a better way to describe it. Its typing is usually considered one of the worst in the game, it can't boost its decent Special Attack, has pitiful physical stats and mediocre abilities. So what's the deal with it? Firstly, the first point isn't all that important in T23 due to the lack of Stealth Rock and Fire, Ice or Rock type Pokémon. It has excellent Special bulk that it doesn't need to invest in to make good use of, letting it focus on bolstering its offenses or physical defense (usually the physical defense). It has good natural Speed, letting it outpace other walls easily and even some offensive threats such as Sentret. Unlike any of its competition as a wall, it has access to the amazing Knock Off which helps neuter opposing powerhouses like Life Orb Skitty and soften the opponent's own defensive backbone by removing Eviolites. There's also its prowess as a bulky setup sweeper, which isn't anywhere as ridiculous as it sounds- both Swords Dance and Curse sets can prove extremely annoying to deal with thanks to their bulk, even if their damage isn't overwhelming. Basically, Ledyba has a number of features that make it a surprisingly tricky barrier for many teams to deal with.

Sample Sets:
1. Swords Dance
Ledyba @ Eviolite
Ability: Early Bird / Rattled
EVs: 252 HP / 252 Def / 4 SpD
Impish Nature
- Knock Off
- Mach Punch / U-Turn
- Swords Dance
- Roost
This Ledyba set can boost up safely against anything that can't 2HKO it, which happens to be a lot of things, and proceed to break down the opposing team. Knock Off is great even when there isn't a good opportunity to boost up for aforementioned reasons. Mach Punch lets Ledyba avoid being revenge killed by the likes of Feebas and Pichu if it has enough boosts, while U-Turn lets this set double as a pivot and provides a single use but stronger attack when boosted. Roost provides this set's longevity. Early Bird makes Ledyba more effective as Sleep fodder, while Rattled can potentially get a boost off a U-Turn and make the opponent's life hell.

2. Curse
Ledyba @ Eviolite
Ability: Early Bird
EVs: 252 HP / 252 Atk / 4 Def
Adamant Nature
- Curse
- Mach Punch
- Knock Off / Sleep Talk
- Rest
This set sacrifices immediate defensive presence and faster offensive presence for a much higher sweeping capability. With the power to bolster its physical defense and also not have to worry about status thanks to Rest, this set can quickly get out of hand if the opponent doesn't have a good way to deal with it. Mach Punch allows Ledyba to entirely ignore the fact that it made itself extremely slow, which is good for sweeping and helps versus the fast frail Special attackers that could threaten to revenge kill it if weakened. Knock Off gives the set utility outside of just sweeping as well as a higher damage move on most targets, and can be afforded over Sleep Talk as Early Bird results in Ledyba only being inactive for one turn. Rest is used instead of Roost as this set's slow startup otherwise makes it vulnerable to Toxic.

3. Pivot
Ledyba @ Eviolite
Ability: Early Bird
EVs: 252 HP / 252 Def / 4 Spe
Impish Nature
- Knock Off
- U-turn
- Roost
- Toxic
Simple but effective, this set excels at taking hits, removing items and keeping up momentum. Toxic is used to offset the set's passiveness and Roost lets it function throughout the battle.

4. Choice Specs
Ledyba @ Choice Specs
Ability: Swarm
EVs: 40 Def / 252 SpA / 216 Spe
Timid Nature
- Bug Buzz
- Air Slash
- Knock Off / Giga Drain
- U-turn
This set is alright on its own but heavily benefits from the surprise factor it brings. Ledyba's damage with Choice Specs is actually quite impressive, OHKOing standard Life Orb Skitty and 2HKOing the majority of the tier with its STAB attacks. Bug Buzz is Ledyba's most spammable and strongest attack, becoming obscenely powerful if boosted by Swarm. Air Slash provides powerful coverage for Bug resistances such as Pidove and Spinarak as well as a chance to flinch the target, which can help with breaking past walls. Knock Off allows Ledyba to remove Eviolites from specially defensive switchins and leaves them 2HKOd by it later in the match, while Giga Drain provides strong coverage that specifically makes this set a reliable answer to Specially Defensive Curse Wooper, a Pokémon that can give many teams a lot of trouble. U-Turn is a big selling point of this set, making Ledyba one of two fast special attackers that can provide momentum alongside Pichu. The provided Speed allows Ledyba to outspeed Hoothoot, Hoppip and Skitty reliably, which leaves enough Defense for Ledyba to take two Fake Outs from Life Orb Skitty 67% of the time from full HP.

Other Options:
Ledyba can invest in Special Defense in order to become an obscene special wall, able to avoid a 2HKO from Choice Specs Pichu's Thunderbolt, but this leaves it vulnerable to the plethora of physical attackers that can easily take down the set. Ledyba can also run a dual screens set, but this requires the sacrifice of either Roost or Knock Off as well as bulk (due to running Light Clay) to be effective, and there aren't too many setup sweepers that abuse screens amazingly in the tier.

Checks and Counters:
Skitty: Skitty can Toxic bulky sets without Rest in exchange for its Life Orb, and can take down the Choice Specs variant with Fake Out + Sucker Punch. Z-Work Up variants don't even fear Knock Off.
Hoothoot: Choice Specs or Work Up Hoothoot variants can easily take down defensive Ledyba with their Flying STAB.
Sentret: Choice Band Sentret 2HKOs any Ledyba variant with Double-Edge and can Knock Off or Trick its Eviolite.
Pichu: Choice Specs Pichu is capable of revenge killing any weakened Ledyba, and can take a +6 Mach Punch if kept healthy.
Toxic: most Ledyba sets are vulnerable to Toxic from anything.