Atomic Samurai is an S-Class Rank 4 hero in "One Punch Man". Atomic Samurai has a long black hair tied in a topknot with dark eyes and a prominent jawline. He is known as the strongest backup hero.
Atomic Samurai has a prideful personality as he refused to shake Saitama's hand as he only acknowledges the strong and Saitama needs to reach the S-Class rank so that Atomic Samurai can greet him. Even with prideful personality, he holds an utmost respect for Bang or Silver Fang, The S-Class rank 3 hero in "One Punch Man".
Atomic Samurai is known as a master swordsman in "One Punch Man". Atomic Samurai is also a skilled teacher as he trains 3 disciples who are in the top five spots in A-Class. Atomic Samurai is really formidable using his sword that his sword attacks are so fast and strong that the enemy are slashed into many pieces in an instant.
Atomic Samurai has an immense speed and reflexes as he was able to cut his opponents to pieces in the blink of an eye using his sword in "One Punch Man". He even manage to dodge Evil Natural Water's attack. Evil Natural Water is a Dragon level mysterious being that has an attack that is fast as bullets where Atomic Samurai was able to dodge it.
Atomic samurai was also able to counter many Melzalgald's attack, another Dragon level Mysterious Being in "One Punch Man" where attacks were extremely quick. Atomic Samurai appears to have an extreme deal of strength. Atomic Samurai can easily cut through solid matter with his sword as well as creating a powerful shock-wave with a single slash.
It is said that his strength is Nuclear Powered and that could be related to his name which is Atomic. Let's wait for "One Punch Man Season" 2 to be released and we see Atomic Samurai Cutting enemies into million of pieces.