Scantily clad warriors without a really good reason as to why they are scantily clad. Aztec warriors may be naked waist up, but knights should be in full armor regardless of gender. Wizards should probably at least have their arms and vital organs covered, and super heroes do not need to be wearing form fitting spandex that only covers their genitals and navel. If a character design has a sleeveless top, have a reason. If a character is wearing a mythril bikini, they better also be wearing something to protect their internal organs or be in a context in which such an outfit makes sense.
To be a bit narcissistic and point to my own character designs for a moment, I tend to dress my characters from neck to ankle in clothes that make sense given their context. In The Bio War, the British super soldiers are wearing British WWII officer uniforms because they are British officers on a recon and damage control mission in Liege, Belgium. The Nazi is wearing an SS uniform and the civilians are wearing casual working class jackets, button-up shirts, and work pants. By the current page, one of the Brits has torn apart the sleeves of her uniform by using one of her abilities, so in the future she will receive a modified combat uniform that has no sleeves, as will the two soldiers with the ability to unhinge many of the bones in their body at will. The character who is about to go super sayan will likely need a drastically modified uniform in the future, but I haven't designed it yet. What I have NOT done is randomly put these characters in spandex and latex uniforms that show off bits of their anatomy that would only be tactically advantageous if the enemy was an army of perverts who were incapacitated by their own dirty thoughts. Also, spandex and latex did not exist in 1941 in the state that they do now, so this would make even less sense.