Evil is not a zero sum resource in <PERSON>'s world that must be apportioned between individual beings. This is made evident throughout his work, for example by descriptions of really evil beings like Melkor/Morgoth or <PERSON> corrupting others. In fact, <PERSON>, once an angelic fire spirit (a Maia) in the service to <PERSON> back when the world was being created in <PERSON>'s legendarium (see "The Valaquenta" in The Silmarillion), was corrupted by <PERSON>.
Another example is the creation of the race of Orcs (as published in The Silmarillion, a subject <PERSON> was torn about in later Letters):
So it came to pass, some years ere the coming of Oromë, that if any of the Elves strayed far abroad, alone or few together, they would often vanish, and never return… But of those unhappy ones who were ensnared by Melkor little is known of a certainty… Yet this is held true by the wise of <PERSON>, that all those of the Quendi [i.e. Elves] who came into the hands of <PERSON>, ere <PERSON> was broken, were put there in prison, and by slow arts of cruelty were corrupted and enslaved; and thus did <PERSON> breed the hideous race of the Orcs in envy and mockery of the Elves, of whom they were afterwards the bitterest foes. For the Orcs had life and multiplied after the manner of the Children of Ilúvatar; and naught that had life of its own, nor the semblance of life, could ever <PERSON> make since his rebellion in the Ainulindalë before the Beginning: so say the wise. 381
And deep in their dark hearts the Orcs loathed the Master whom they served in fear, the maker only of their misery. This it may be was the vilest deed of <PERSON>, and the most hateful to <PERSON>. (emphasis added)
—The Coming of the Elves and the Captivity of Melkor, The Silmarillion
<PERSON> was not made less evil, or more good by creating the Orcs, but their creation was a manifestation of his evil. Indeed, <PERSON> described all evil in the world as having its origin ultimately in Melkor. <PERSON> never describes such acts as redistribution of evil as a finite resource, but as the creation of new evil where it did not exist before. 736