Lilith from Tokyo Babel, maybe? If Touma doesn't do dragon shenanigans, she just kicks his ass with superhuman stats. If he does use dragon shenanigans, her always-on ability means he'll never hit her because every instance of someone interacting with her is a hyper-realistic illusion, so he eventually tires out(well, unless he now has infinite stamina, in which case she can't win, but certainly won't lose).