There's no Katekyo Hitman Reborn , Beezelbub , or Toriko

I'm suprised you don't the god level op characters of Yuki Nagato and Kyrie Illunis on this list.  Nothing in those anime can even touch their levels of power and few characters in all of anime history even come close.  They are essentially on the power level of gods and goddesses.  And I have them at the top of my op characters list of all time, though I titled the list differently.  Though some on your list I could agree on, I would not concur on their position.  I'd rate 7 Deadly Sin's Melodias higher than Full Metal's Edward or that weird kid god like enemy who I think was the better and more powerful enemy of either series' of Full Metal and Claymore.  A few others I would have adjusted to but most are a bit closer a call.  Claymore there are several characters from that series that are exceptionally powerful so even though some are pretty broad a margin in power, they are generally closer together in power than say Melodias to nearly anyone in Deadly Sins.  Claymore for example has a whole group of 'awakened' where as we only know of a dozen or so demons existing at all.  Though Ban is pretty powerful to, I think he isn't actually quite an equal match. Even if he were, the last remaining sin is the strongest for brief time periods supposedly but has far more weaknesses too.  So it really isn't quite better than Melodias.  This is the same for Hunter x Hunter, though Gon might have the most potential, he is far from the strongest and there are half a dozen to a dozen on a level comparable to him or better even at his strongest.  Two of his buddies for example could be on that list.  Two of the bug queen's children would be on that list for sure but if the king had more time to live and grow, he might have well surpassed Gon's greatest potential or perhaps he had a finite upper limit.  One of the methods of his growth was too vague even if it appeared quite op and gross.  The queen's method of creating new life was even more op.  Those higher level characters and skills had kind of a quirky balance that some what offset each other though so the differences might only appear greater then they were.

I roughly agree that most belong on such a list and it is a good list but there is quite a few more you could add and a few you could add that would put them all to shame.

One-punch man is another (and the whole point of the story)