While little is known about Saitama's background, he didn't seem to have a lot of friends growing up. In fact, he was often disliked and bullied by the people around him. It could even be said he came to a point where he embraced a hermit-like lifestyle.
But as the series goes on, from the web manga to the anime, he connects with various allies who leave a great impression on his life. Even characters who seemed to outright dislike Saitama at first often find themselves starting to like, or at least respect, "Caped Baldy." On the other hand, just because Saitama managed to win over some characters, it doesn't necessarily mean that they have their respect in turn.
10 Suiryu: Even After The Clothing Incident, Saitama Still Inspires Him
Suiryu and Saitama have a complicated relationship. Saitama originally respected Suiryu's abilities and wanted to get a better understanding of his martial arts prowess. Unfortunately, Suiryu's low opinion on heroes caused an altercation between the two, leading Saitama to destroy Suiryu's clothes.
Despite this altercation, Saitama was willing to protect Suiryu during a fight and was even impressed with how long he held out. Saitama has faith that Suiryu could become a hero, although he wasn't willing to take Suiryu on as an apprentice.
9 Forte: At The Very Least, He Knows To Stay On Saitama's Good Side
Forte is the type of character who soon realizes it's best to stay in Saitama's good graces, if only for practical reasons. Forte is one of Saitama's neighbors in Z-City and thought little of him, even using his status against him.
Eventually, however, Forte would recognize he and his accomplices couldn't match Saitama's level, causing him to try to get on his good side and apologize for his previous behavior. Forte has also been known to warn his accomplices about Saitama's prowess.
8 Flashy Flash: He Even Wanted To Train Saitama
Saitama really doesn't have much luck with first impressions; Flashy Flash mistook him for a monster and tried to attack him. But Flashy Flash soon realized the truth and even became impressed with Saitama. Noting how basic Saitama's style really was, Flashy Flash even wanted to teach him some techniques.
For his part, however, Saitama admitted he found Flashy Flash annoying and has even had difficulty remembering the hero's name.
7 Sweet Mask: He Became A Little Too Obsessed With Saitama
Like many characters, Sweet Mask, also known as Amai Mask or Handsome Kamen, originally underestimated Saitama as a lower-class hero. After all, Sweet Mask tends to give too much credence to appearances. After seeing Saitama in action, however, Sweet Mask starts to not only respect Saitama, but become outright obsessed with him and plans to groom him into a suitable hero.
Unfortunately, things are a bit more complicated than him having a change of heart: believing his own monstrous nature will keep him from being the hero he thinks the world needs, he wants Saitama to kill him to take on the mantle of being the ideal hero.
6 Zombieman: He Wants To Be More Like Saitama
Zombieman and Saitama start off having different feelings about each other. Saitama was interested in the stories of Zombieman's immortality, although he wasn't sure if they were true or not. For his part, Zombieman seemed to dislike Saitama over his rank and refused to believe stories about his prowess, even thinking it was a joke.
Eventually, however, Zombieman's thoughts on Saitama change after seeing him in action and realizing the stories about him are true. It gets to a point where he wants his limiter removed in the hope of becoming equal to Saitama. He's also shown concern for Saitama's safety at times.
5 King: He And Saitama Even Play Video Games Together
Out of context, King seems like the kind of person who would be Saitama's ultimate rival, since being in the right time and place usually gets him the credit for heroic deeds that rightfully belongs to Saitama. But as Saitama has saved King many times from various threats, King greatly admires Saitama and feels incredibly guilty over being seen as the hero Saitama truly is.
Fortunately, as Saitama isn't one to hold grudges over such petty misunderstandings, the two form a friendly bond as they start getting to know each other. They even play video games together. Unfortunately, as gaming is one of the few things King actually is good at, Saitama does get frustrated over losing to him.
4 Fubuki: Saitama Seems To Be A Good Influence On Her
Upon meeting Saitama, Fubuki wanted him to join her group, but eventually decided to join his group instead. As she gets to know Saitama, Fubuki starts to show her softer side.
Saitama seems to have a good influence on her, as she wants to become a better person and even stand up to her sister, Tornado, after befriending him. Despite this, she still likes to keep up the appearance of Saitama being her underling, though he actually outclasses her. For his part, Saitama can get annoyed by her, but there's still a strong affinity between the two.
3 Bang: He And Saitama Are At Least Social With Each Other
Bang took an interest in Saitama's abilities and began to spy on him, although this caused him to make a few wrong assumptions about him, not even realizing Saitama was self-taught and doesn't really use a technique. Upon fully grasping Saitama's potential, he sought to recruit him for his dojo, an offer Saitama just wasn't interested in.
Just as Bang has a lot of respect for him, Saitama has shown to have some respect for him in turn, as well as confidence in his abilities. On the other hand, Saitama once almost killed Bang over a game. That said, the two are social with each other, even inviting each other to cookouts.
2 Mumen Rider: These Two Even Have A History, Not That They Realize It
Mumen Rider is one of the few characters who acknowledge Saitama's real strength and respects him. He even once went out of his way to send a thank-you letter to him. For his part, Saitama respects Mumen Rider's abilities, compliments him at times, and even once visited him in the hospital.
Apparently, the two have a history, as they were once classmates. They don't seem to realize this, though, suggesting they didn't interact at the time.
1 Genos: The Closest Person To Saitama Is His Apprentice
Saitama first met Genos after he saved the cyborg from trying to self-destruct after being defeated by a monster, Mosquito Girl. After saving him, Genos aspired to become Saitama's apprentice, something that Saitama begrudgingly accepts before eventually warming up to him.
Saitama doesn't really refer to Genos as his disciple, but does play along with the idea to humor him, even when there's nothing he can really teach him. Even so, there are a few times when he even managed to give him good advice, has confidence in him, and goes out of his way to protect him.