This is one character who seems to pop up only occasionally, but I remember when they tried reviving her during the Anime Boom of the 1990s. I never did see the original version of her by Go Nagai, so I only remember a short-lived OAV series and comic adaptation. Pretty interesting take on the character.
From what I saw of Nagai's manga, it'd have to be serious. It seems that the theme was akin to his Devilman and giant robo stories, where the protagonist is literally the last line of defense against some seriously nasty villains.