Obito, Madara, Sasuke, Itachi, Jiraiya
In jutsu effectiveness = Itachi and Sasuke Amaterasu
This jutsu is hard to counter and put off unless the person is Juubi jin or have kamui
That effectiveness making Amaterasu is best fire jutsu to disable many opponent, make them making risky decision like Ay where
he need to cut off his sever arm or Juubi needed to separate his body part(he is lucky to have that ability), use for distraction, and among other
It ability that can't be put off, slow burning but it will spread to whole body later, contagious in nature.
Is the potency that show by this unique fire technique.
Madara and Obito katon and bakuufu Ranbu is just dependable on the size to get effective.
But it lack many great feature of Amaterasu.
Effectiveness is important here although just small in scale
Peace