Answer: Well, if we're talking Superman circa 1993 through 1996, that would be a MULLET! Yes...the legendary hairstyle of skeezy hicks, trailer park lotharios, and 80% of the perps on COPS was shared by none other than Superman for not one year...not two years...but an interminable three years!
It's hard to exaggerate just how bad the early 1990's were for comics. From the glut of gimmicky special-effect covers to the crass dimwittery of Image Comics, even time-tested icons like Superman found themselves subjected to the fad-chasing desperation of those utterly clueless, creatively vacant times.
To set the context, when Superman was "resurrected" following his much-ballyhooed death earlier in '93, he emerged sporting a dark bodysuit and...what's this?...shoulder-length hair? Nervously chalking it up to an effect of his long hibernation, I assumed Kal-El would get a trim. Ah, but since this was the creatively bankrupt DC Comics of the early 90's, the powers-that-were inexplicably made the Super-Fabio look permanent!
Here's a few covers from that seemingly-endless three-year time period...
which, even now, make me want to never stop screaming.
(if you're a glutton for punishment, click to enlarge)
To be fair, not every Superman artist at the time seemed to embrace the new "luscious locks" directive with equal enthusiasm. Some (like Dan Jurgens) drew the hair only slightly longer in back...giving it sort of a "semi-mullet" or "mullet-wannabe" look...but others, like Jon Bogdanove and Stuart Immonen, went completely bonkers and drew Supes with a buffoonish lion's mane of swirling, cascading hair...which transformed a symbol of classic manly power like Superman into a boho, bizarrely feminized imposter.
Of course, just around the corner from Mullet Superman was the equally ill-advised Electro-Superman, yet another desperate Hail Mary pass from the creative titans of the mid-90's DC Comics. But, as painful as the continuation of Superman's "Steaming Pile of Crap" phase was, it was still better than facing the nonsensical spectacle of a mullet-sporting Man of Steel.
After all, you'd think he'd learned the pitfalls of hippy-hair way back in Superman #139 (1960), when Red Kryptonite transformed him into a "Super Wild Man from Borneo"!