The battle between Mailman and Undyne The Undying was a fierce one, but ultimately Undyne emerged as the clear winner. The Mailman had some impressive skills, like Special Delivery Today, which allowed him to throw bombs wrapped in boxes, and Return to Sender, which let him send back attacks. But Undyne's training as a Royal Knight and her heroic mindset gave her a major advantage in the fight. Undyne's weapon, conjured spears, proved to be particularly useful in this battle. She combined her spear attacks with magic to create devastating spear/magic combos, overpowering the Mailman's guard. Additionally, her high guard and magic guard made it difficult for the Mailman to successfully attack her. Even when he attempted to use Boxcutter, Undyne's training and experience allowed her to easily dodge and counterattack. Furthermore, Undyne's healing factor was a major advantage in the battle. Though the Mailman had the skill Doordash, which allowed him to heal by ordering food off of Doordash, Undyne's healing was innate and allowed her to quickly recover from any injuries she sustained. Finally, the Mailman's ultimate mailing art, You've Got Mail, proved to be his downfall. While this skill could have been useful in summoning other mailmen to help fight, in this case it only served to distract him and allow Undyne to land final blows. All in all, while the Mailman was a worthy opponent, Undyne The Undying's strength, training, and heroic mindset allowed her to come out on top in this battle.