Akuma is not a ‘mortal’ figure. He has transcended humanity and is Asura-like, hence the Heaven kanji. Being ‘beyond humanity’, however, does not necessarily mean closer to enlightenment. Tantric Buddhism is not 100% in line with standard Buddhist practices and Wrathful Practice is not the same thing as the path of the Asura or the state of reincarnation as an Asura (Akuma’s current being). Akuma is drenched in negative karma and is ignorant of his failure. Wrathful Practice, even if it were to be applied to Akuma, would further reveal him as a failure because, in his arrogance, he presumed to know what should and should not be destroyed.
He destroys things that do not need to be destroyed out of acts of egotism and vanity. He believes destroying other fighters makes him better and proves that. This is an ignorant, transient view because victory in the moment is not victory in eternity. By killing fighters he prevents them from improving which, in turn, prevents Akuma from having the opportunity to further improve.
His hypocrisy is even more thoroughly revealed via Ryu…because he feels Ryu can improve and challenge him, he lets Ryu live but ONLY because Akuma sees in Ryu the power that Akuma himself has. This is a further act of vanity because Akuma only recognizes potential greatness when it mirrors himself. This is not a methodology that can ever lead to enlightenment as it is rooted in the self. Similarly, his ‘mercy’ towards Gen was also an act of vanity. He did not spare Gen out of a sense of actual mercy but rather as an act of vanity because killing a sick foe was “beneath” Akuma.
The ultimate fate of Akuma and his path of the fist is well illustrated (literally and figuratively) in Ryu Final. He recognizes his utter failure as a martial artist and that he was entirely wrong about essentially every thing in his life. He is (again literally and figuratively) hollow inside, cored out by his negative karma, incorrect path in life and his egotism. Akuma’s fate is not to ever be enlightened on his current path. The Asura is an undesirable reincarnation and it speaks of obsession with vanity, wrath, violence and egotism (Akuma in a nutshell). It does suggest a person may have had good intentions, but their actions were overwhelmingly negative. Again, Akuma’s path is admirable…the path of the true martial artist is a potentially virtuous and admirable thing…but Akuma has never been right about a single thing in it.
Ryu, on the other hand, makes mistakes and learns from them. He improves and adapts. As a ‘human’ still, he always remains more capable of enlightenment despite being less powerful than Akuma. It is always nearer to him than Akuma despite Ryu’s missteps because he is still human and a human incarnation is more desirable than that of the Asura.
“ I have transformed myself into an enlightened, wrathful being.”
This is exactly Akuma’s failing that he is forever trapped in and why he can’t become enlightened.
In fact, the only way he could ever reach enlightenment is more than likely through Ryu’s fist and through rejecting everything he has ever done after seeing the utter failure of his previous efforts. His karma would still need to be accounted for, however, so, more than likely, he would have to live a life of virtue and wisdom. A good example of this character archetype would be Liu Zongwu from Fist of the Blue Sky