I suppose that with such a question in this particular text, I would say that the only way the good ends up dominating evil is that everyone (including evil) ends up dying. The way Shakespeare has configured the play, the ending is not especially redemptive. Lear, who has gained insight into what true love and devotion mean, and Cordelia, whose loyalty and honor never wavered, both end up dying. The potential advantage would be that the malevolent forces exhibited through character such as Regan and Goneril also end up dying, as well. If there is the hope of good triumphing over evil, it is present in the basic tenet that Lear does recognize truth and that the element of transparency and honesty is acknowledged for a moment before events spiral out of control where death is the final result.
There is more to this question than you might imagine. Traditionally, it has been thought that in the character of Cordelia, Shakespeare has good win out over evil. In spite of her terrible treatment by her father, she rallies her troops and tries to help Lear regain his kingdom. They restore their fractured relationship, but she dies, he dies, the kingdom is still a mess in the end.
I really like the analysis here on eNotes that explores an alternate interpretation of King Lear as "an absurd, nihilistic vision" because in my view, the ending of the play has always been unsettling to me when viewed through the traditional interpretation. If Cordelia had lived, and Lear had lived, and the kingdom had been restored, and Lear had admitted to Cordelia that her love redeemed him, then maybe one could say that "good" wins in the end. Good, though it exists, does not seem to be strong enough to redeem anything in this play, so it is very depressing in the end and one does not get that "fuzzy, feel-good" feeling.
I don't agreed that good always wins in the end in literature. This only happens in fairy tales, and then not even always in them either. As long as evil exists in the world, there is going to be the constant battle of good vs evil. Sometimes good wins, sometimes evil wins, in THIS world.........
What do you think? Read about it here on eNotes.