Ninja Gaiden Sigma

Basically, when the fight starts, the dragon will bring his head toward you, that will give you a few free hits. After that, hit the ground switch to raise the platform and head to the left most platform.

From there, stay as far left as you can, so you won't be bitten and chewed, and charge up an ET or UT. I found Dabi to be the most useful for this fight, but I believe some people have said the dragon sword works too.

Then, the only attacks you need to worry about are the flapping wings and fire breath.

When he flaps his wings, all you have to do a roll. Try to roll forward or backwards as rolling to the side puts you in line to get chomped.

When he does the fire breath, just time a jump to go over it. Once you land, quick charge your ET/UT again and repeat as necessary.

If you miss the timing on anything, don't get discouraged. Just keep trying and before you know it, there's one dead dragon in front of you.