One Punch Man is one of the most popular anime to appear in the past decade. One of the things that makes it so great is its excellent cast of characters.
Who are the best One Punch Man characters? Some obvious contenders are Saitama, the protagonist who can defeat anyone with a single punch. There's also his cyborg protege, Genos, or his "rival" Speed-o'-Sound Sonic. Prefer more blatantly villainous characters? There's Lord Boros, the ultimate villain of the first season who came to Earth to seek out someone who could take him on in battle. Whatever your preferences, there will be at least a few characters on this list that you vibe with.
This list will only look at characters who either appeared in the first season, like Tatsumaki, or who have been definitively announced for Season 2, like Garou. The manga and webcomic are filled with amazing characters, but since they've yet to appear in the anime, they won't be appearing here.
Saitama is the protagonist of One Punch Man. Despite incredible strength that allows him to defeat anyone with a single punch, he isn't arrogant about it - he cares more about clipping coupons and relaxing with a good TV show than what anybody thinks of him.
Genos is a powerful cyborg who trains under Saitama. He's one of the only people who actually understand how strong his mentor is, and wants other people to appreciate him too.
Garou is one of the major villains in the second season of One Punch Man. He hates heroes and wishes to destroy them, but his reasons for doing so are less theoretical than they are personal.