Did Edmund show any positive qualities in King Lear?
From the beginning of the play Edmund is well regarded for his good looks and polished manners. When his father introduces him to Kent in the opening scene of the play Gloucester seems slightly embarrassed that Edmund is a bastard. When he asks, "Do you smell a fault?" Kent politely responds:
I cannot wish the fault undone, the issue of it being so proper.
Lear's daughters Goneril and Regan also find Edmund very attractive, and by the end of the play they are both quarreling over him. Regan is free to marry him, since her husband Cornwall was killed; but Goneril is scheming to have her own husband Albany killed and expects to be free to marry Edmund herself. Edmund may be a villain, but he is a charming one. He knows he has to advance in the world on his own merits, and he is doing so very effectively. Goneril and Regan care little about his shady character, since they are not too different from him in that respect themselves.
Edmund's character seems to improve towards the end of the play. He seems less of a villain and more of a nobleman. This no doubt is due to the fact that he has succeeded in eliminating his brother Edgar as an heir to Gloucester's title and has managed to usurp it by betraying his father to Cornwall. In Act III.5 Edmund says hypocritically:
If the matter of this paper be certain, you have mighty business in hand.
True or false, it hath made thee Earl of Gloucester.
As Earl of Gloucester, Edmund must feel that he is in the public spotlight and must act the part. He also feels like a different person, having attained high status and seeing the prospect of enjoying even higher status if he marries one of Lear's daughters. When Edgar appears in V.3 and accuses him of treason and challenges him to a trial by combat, Edmund responds with noble dignity.
In wisdom I should ask thy name;
But, since thy outside looks so fair and warlike,
And that thy tongue some say of breeding breathes,
What safe and nicely I might well delay
By rule of knighthood, I disdain and spurn:
Back do I toss these treasons to thy head;
With the hell-hated lie o'erwhelm thy heart;
Which, for they yet glance by and scarcely bruise,
This sword of mine shall give them instant way,
Where they shall rest for ever. Trumpets, speak!
And after Edmund has been mortally wounded, he shows that there is a good side to his nature when he repents and says:
I pant for life. Some good I mean to do,
Despite of mine own nature. Quickly send--
Be brief in it--to th' castle, for my writ
Is on the life of Lear and on Cordelia.
Shakespeare seems to have intended to show that Edmund's father was punished for his sin of adultery. The product of that sinful relationship was a man who inherited his father's noble qualities but tainted by his father's guilty behavior. Edmund's villainy is the natural result. But he possesses positive qualities, including courage and intelligence, and he demonstrates a sense of honor at the end of the play. He is one of the most interesting characters in King Lear. Directly or indirectly, he touches the lives of all the other major characters in the play.