Take a big prybar and hammer to it if you like, but then go buy an entirely new adjuster assembly, if you don’t break the deck. I would remove the white clutch washer, black seal ring and wipe the grease off. You will then find an E-clip which is holding the adjuster to the shaft. Remove and the adjuster will come off. I hope you are noticing the direction each part comes off, as they need to be replaced as taken off.