Now, for sure I am not 'too' good at Geometry Dash, but Medium Demons are the farthest I can get.
The one's I've completed are..

Ultra Violence by Xender Game

Nantendo by Im Fernando (This one was 5 minutes long, one wrong move and I went back to the very start..)

And Gear III by GD Jose

The only honorable mention is an Easy Demon called Change of Scene by Bli, in which I don't have a picture for.. But I have a video of it on my YouTube!