After pretending to be a possessed homeless man for most of the play, Edgar cures his father Gloucester of being Driven to Suicide by tricking him into thinking that he's jumped off a cliff, and then goes on to win a swordfight against the Magnificent Bastard (literally) Edmund. And all is right in the land! Kinda.
This troper has always loved the First Servant from that play. A nameless servant of Cornwall watches sees his master gouge out Gloucester's eyes, and draws his sword, shouting:
Hold your hand, my lord!
I have served you ever since I was a child,
But better service have I never done you
Than now to bid you hold.
He then duels his master and fatally wounds him, dying only when Regan stabs him in the back. This was a completely nondescript background character, defeating and killing one of the villains for no reason other than a sense of right and wrong that most of the play's named characters lack.
Kent's absolute evisceration of Oswald in 2.2.
Oswald: What dost thou know me for?
Kent: A knave; a rascal; an eater of broken meats; a base, proud, shallow, beggarly, three-suited, hundred-pound, filthy, worsted-stocking knave; a lily-livered, action-taking knave, a whoreson, glass-gazing, super-serviceable finical rogue; one-trunk-inheriting slave; one that wouldst be a bawd, in way of good service, and art nothing but the composition of a knave, beggar, coward, pandar, and the son and heir of a mongrel bitch: one whom I will beat into clamorous whining, if thou deniest the least syllable of thy addition.
Oswald: Why, what a monstrous fellow art thou, thus to rail on one that is neither known of thee nor knows thee!
Kent: What a brazen-faced varlet art thou, to deny thou knowest me! Is it two days ago since I tripped up thy heels, and beat thee before the king? Draw, you rogue: for, though it be night, yet the moon shines; I'll make a sop o' the moonshine of you: draw, you whoreson cullionly barber-monger, draw.
And let's not forget slightly later:
Kent: Thou whoreson zed! thou unnecessary letter! My lord, if you will give me leave, I will tread this unbolted villain into mortar, and daub the wall of a jakes with him. Spare my gray beard, you wagtail?