What you are looking at is the left side bearing cone. There should have been a keyed washer and lock nut on top of what you see. Did you remove these already? The threads on this side are left-handed meaning that to remove, you need to turn them clockwise. Bearing cones should not be cranked down tight and so should easily unscrew. The last couple I did unscrewed with just finger pressure. If yours is rusted or crudded up it may take a bit more effort. Squirt some penetrant onto the threads and wait a few hours, then grip the flats with a pair of pliers (or whatever else comes to mind) and turn clockwise. If that still doesn't work, I'd probably tap on the flats with a chisel and hammer (again clockwise!) until it breaks loose. You'll probably replace the bottom bracket anyway so hammer away. Just don't damage the threads on the crank.
Good luck.