He's by far the hardest Blight. Go to Faron Woods east of the desert, pick some hearty durians, and give yourself some extra health by cooking them. If that doesn't work, go do shrines and level up your armor and health.
Learn the patterns. Perfect dodge/parry the sword attacks for the first half. When it summons its metal spikes use magnesis on them and move it towards it so it gets stricken by its own lightning.
Also bring strong weapons to chop away at his shield. Parrying and blocking attacks can be tricky but thats what you have to do before you strike. He worked me quite a bit but don't give up.