I’ve got to add the confession in American Psycho - some of the finest acting I’ve seen.
Sick Boy’s Unifying theory of life, not grand but good anyway.
Thomas Colpepper, JP: *Well, there are more ways than one of getting close to your ancestors. Follow the old road, and as you walk, think of them and of the old England. They climbed Chillingbourne Hill, just as you. They sweated and paused for breath just as you did today. And when you see the bluebells in the spring and the wild thyme, and the broom and the heather, you’re only seeing what their eyes saw. You ford the same rivers. The same birds are singing. When you lie flat on your back and rest, and watch the clouds sailing, as I often do, you’re so close to those other people, that you can hear the thrumming of the hooves of their horses, and the sound of the wheels on the road, and their laughter and talk, and the music of the instruments they carried. And when I turn the bend in the road, where they too saw the towers of Canterbury, I feel I’ve only to turn my head, to see them on the road behind me. * - Powell and Pressburger: A Canterbury Tale
The Lion in Winter:
John: It’s not so hard. Try saying after me; John wins, I lose.
Richard: What if John died?
John: What’s that?
Richard: What if he left us suddenly?
John:You wouldn’t dare.
Richard: (going for his dagger) Why on earth wouldn’t I?
John: A knife! He’s got a knife!
Eleanor of Aquitaine: Of course he has a knife. He always has a knife. We all have knives. It’s 1183 and we’re barbarians. How clear we make it. Oh, my piglets, we’re the origins of war. Not history’s forces nor the times nor justice nor the lack of it nor causes nor religions nor ideas nor kinds of government nor any other thing! We are the killers; we breed war. We carry it, lke syphilis, inside. Dead bodies rot in field and stream because the living ones are rotten. For the love of God, can’t we love each other just a little? That’s how peace begins. We have so much to love each other for. We have such possibilities, my children; we could change the world.
Reading your OP, that’s exactly what popped into mind. I think it’s one of the best ever and am glad to see I’m not alone.
For a completely wordless “monologue,” how about Milla Jovovich’s scene in The Fifth Element where, as a complete innocent, she first learns about war?
The climatic speech from The Great Dictator (the speech itself starts ~1:00 in.)
It’s too long to quote, but when you get a few spare minutes to watch it, do so…it’s chilling.
There’s even a couple “mashup” versions that I like that set it to music:
Set to the music from Inception.
Set to the music from 28 Days Later.
Another of my favorite monologues:
“I’m mad as Hell, and I’m not going to take this anymore!”
If I were the man I was five years ago, I’d take a flame-thrower to this place!
How about Dennis Leary as Edgar Friendly in Demolition Man, explaining how he became an enemy of the system:
Not a movie monologue, but rewatching Season 1 of The Shield I came across this and thought it qualified.