Score: 7,000-9,000 This deck is the most consistent with high score but requires some cards that are currently unobtainable.
Score: 7,000-8,000 Piranha Army is needed to get a high score, but it can be replaced with a different card to reach over 5,000 damage for 6,000-7,000.
Unhappy Girl/ Union Attack
Score: 6,000-8,000 The Unhappy Girl + "Holy Guard" will make stalling the duel very easy, and you can bring any high attack monsters if you have Union Attack to finish with over 10,000 damage.
Decks for new players
Unhappy Girl/ Deckout
Score: 5,000-6,000 A slow playstyle with the aim of decking Pegasus out. It doesn't contain any cards from the old packs.
Dino/ Cu Chulain
Score: 5,000-6,000 Cheapest deck to make for newer players that can also achieve a good score.
Dinosaur / Cu Chulain
This is the cheapest deck to farm Pegasus Lvl 40 probably. Although win rate is not high relative to other farming decks with the Unhappy Girl or Dream Clown, it will work for you who did not roll the 1st and the 2nd card boxes and started the game recently.
If you have a copy of Union Attack, you can build a deck derived from high score clown deck by replacing ritual monster and ritual spell with Union Attack and Grave keeper's Vassal. For more details, check the link below.
Similar to the usual high score Cerberus deck, but for Pegasus, it's better to put some Twisters and Trap Jammers to help protect yourself against the Toon Monsters and counter the Michizure or Curse of Anubis.
They cannot attack during the turn when they are summoned.
They can attack your Life Points directly if Toon World spell is active, unless you control any Toon monsters.
A player who controls the Toon monsters have to pay 500 Life Points to attack with some of the Toon monsters.
Toon monsters are destroyed when they are face-up on the field and Toon World spell is destroyed.
Cards to coutner Toon monsters
Dream Clown and cards that have effects similar to that of Dream Clown work very well to destroy/return Toon monsters since they cannot attack right after they are summoned. To make it sure, you may use support cards such as Earthquake to change the battle position of Dream Clown and Windstorm of Etaqua to defend it from being attacked.
When the battle possition of this monster switches from Atk to Def, you can destroy one monster card. Since Toon monsters are unable to attack the turn they're summoned, you can easily destroy them with the effect of this card.
Guardian Statue is the best among cards here since it can return Pegasus's monster to his hand every turn.
"Toon World" spell card
If you just want to defeat him, use Twister or other spell removals to destroy his Toon World. Any face-up toon monsters will be destroyed, and Pegasus will no longer be able to special summon some toon monsters, or attack directly.
Note Pegasus may use Judgment of Anubis to negate the activation of your spell removal card. Additionally, he has another Toon World.