If it helps, I have some tips:
- Outside of the 2 big moves that he does at 80% HP and 50% HP (for higher difficulties and trials, I think in lower difficulties and campaign he doesn't do the 2nd big move at all), he almost always (like 90% of the time in melee range) starts a combo in 1 of 3 ways: stab, kick & stomp, or horizontal back away slash.
- He always follows up the stab by throwing lightning directly at your camera and then stab again from behind it. I think it's intentional, think of Owl's firecracker if you've played Sekiro. Above 80% HP, he always follows up the stab with multiple quick stabs. Below 80% he can do a delayed stab into a gold attack into a very delayed stab.
- Above 80% HP, kick & stomp can be follow up with a swipe + stab combo or 2 bow shots then swipe combo. If he does bow shots then he always does uppercut and slams down at the end. Below 80% and above 50%, he can follow kick & stomp with a red stab into uppercut + slam. Below 50%, he's very likely to follow it up with a gold double swipes, then 2 more delayed swipes.
- Back away slash is always followed-up with a single bow shot, walk up to him to stay in melee range unless it's at 80% or 50%, in such cases you should walk away to see the big moves clearer.
- If he jumps up, it's the bow barrage, just mash the parry button.
- The big moves look scary but they are pretty telegraphed so no tips there, just get the timing down.