Arrancar
Ulquiorra Schiffer
Ulquiorra was the second Espada Ichigo encountered (Yammy was the first), and for the majority of his interaction with Ichigo, doesn't see him as a threat. Ulquiorra is confident that Ichigo's wildly fluctuating power levels will eventually destroy him. Ichigo initially didn't have much of an opinion of the "Cuatro Espada" until he kidnapped Orihime, upon which Ichigo acquired a great dislike of him, though Ulquiorra's opinion of Ichigo remains. In their first fight, Ulquiorra didn't sustain any injuries despite not even drawing his sword and facing a full-powered Ichigo (though, it should be noted that Ichigo burned up his spirit energy in his fight with Dordonii). This battle leaves Ichigo temporarily dead and Ulquiorra with a slightly tattered uniform. After Aizen seals off all of the Gargantua portals, he draws his sword to face Ichigo in combat, prompting Ichigo to ask if he considers him a worthy opponent. Ulquiorra's response is that he sees him as an enemy that needs to be eliminated, and Ichigo claims that it's "good enough for [him]".
Grimmjow Jeagerjaques
Ichigo and Grimmjow have, without a doubt, the greatest rivalry depicted throughout the series. Grimmjow and Ichigo both have a certain respect for each other, despite the ferocity of their fights. Though they have nearly identical personality traits, their fighting styles and motivations are different; Ichigo is a duelist (swordsman), whereas Grimmjow is a brawler (melee fighter), and has yet to learn Kido and Hakuda from Kisuke and Yoruichi. Ichigo also fights for his friends and family, whereas Grimmjow is fights for his own benefit, going so far as to repeatedly disobey Aizen's orders by invading Karakura Town without authorization, allowing his Fracción to die during the battle without a shred of remorse, openly disrespecting one of his superiors, and attacking one of his "comrades", in order to satisfy his need for vengeance against Ichigo. During their third fight, after Grimmjow was defeated, Ichigo grabbed his wrist and gently put him on the ground, with pity in his eyes, and chose not to finish him off. Additionally, after Grimmjow arose from the ground and attacked Ichigo again, he practically begged Grimmjow to "let it go" and stop fighting, now that he has been defeated. Grimmjow, however, stubbornly refused to "give in" and was unexpectedly blindsided by Nnoitra, prompting Ichigo to defend him from Nnoitra's second attack and berate the latter for attacking a defenseless opponent. It is still unknown whether Grimmjow is alive, and if he is, whether his attitude towards Ichigo has changed after his decision to protect him from Nnoitra.
Neliel Tu Oderschvank
When Ichigo first encounters her, she is a young, child-like, amnesic Arrancar kid chased by her former Fracción, Pesche Guatiche, Dondochakka Bilstin and Bawabawa. After Ichigo rushes in to rescue her, it's revealed that they were playing "eternal tag". Nel usually acts as a sort of younger sibling to him, which somewhat annoys him. Though, when he isn't being manhandled by Neliel, Ichigo considers her a valuable friend, particularly when she's in her adult form, due to her ex-Espada status. She somehow retains her child-like affection for Ichigo even as Neliel.
