All I could do was feel the pain.
I have a couple of hills with 18% grades for a short bit. I can do those. Once it gets in the twenties, well, only twice have I been forced to walk. I actually think I could do one of the ones I walked, but the other... it was at least a mile of 18-25% grades, followed by a flat and then another 10-15% grade. I walked the 18-25% part, or at least part of it and did the second part of the hill. I could barely finish the rest of the 15 mile ride. I am used to steepish grades, but they are usually short.