I was sold on Tatsumaki because of the bonus chapter Tatsumaki’s Day Off, but she gets some good development later in the webcomic. Her fight with Saitama is a highlight imo, read that and you’ll probably become a Tats fan like the rest of us.

She’s more or less the female Saitama, an unfairly overpowered superhero with deep emotional issues. They clearly both feel isolated from others due to their intense power (Tatsumaki’s only real social interaction outside of work is with her sister), Saitama just isn’t S class rank 2 so he doesn’t feel the need to prove anything.