A few things should be mentioned beforehand:

I tried to shoot down the helicopter first to get a no damage fight. However, it spawns again and again. So, the helicopter shot me during the whole fight. I can't do anything about it without disturbing the flow of the fight.
I can't cut Sundowner's shield with the Wooden Blade. Therefore, this whole fight consists of the first phase. But maybe I have a surprise for you at the end of this video ^^

Rules for this challenge (gameplay restrictions):
Wooden Sword only (completely downgraded)
Only light attacks (X-Button spam on the Xbox controller)
No Skills (especially no "offensive defensive")
No Ripper mode
No Blade mode (except for the boinks at the end)
No Wigs
No Secondary (Unique) weapons
No Sub weapons
(Of course) No heal or items of any kind
No attacking while he is holding the pole
Last but not least: No Damage from Sundowner (except the chopper)

Difficulty: Revengeance (highest Difficulty)

Note: In case, if you're wondering why the 300 combo isn't included in the main gameplay. I managed to do this in one of my earlier attempts. Overall, the combo is interrupted when the chopper shoots at me for longer. In my final attempt I was unlucky with the chopper, so unfortunately I couldn't make such a high combo again.

Timestamps
0:00 Explanations
0:45 The Fight
9:52 The Surprise
10:10 Another Fight (Second Phase)

Enjoy!

Metal Gear Rising PC Gameplay
Raiden vs Sundowner only Woodensword (downgraded) No Boss Damage Revengeance Difficulty
Red Sun over Paradise