Dynasty Warriors 9 - Wang Yi - Level 1 to 100 - Ultimate Difficulty

Equipment
Dark Piercer EX (ATK 528 / DEF 96)
Gems (Slash)
Speed +5
Attack Speed +5
Attack +33% with elemental
Defense +80% with elemental
Musou +7/sec. with elemental
Attack Speed +9% with elemental
Trigger Attack +20%
Flow Attack +32%
Mounted Damage +27%
Special Attack Damage +87%
Musou Attack Damage +75%
Elemental Attack Damage +3 during a Counter
Elemental Attack Damage +2 during a Guard Break

Accessories
Heaven & Earth Gauntlets (w/ Allows you to jump at any time while attacking)
Warrior's Plate (w/ Speed +13)
Warrior's Plate (w/ Speed +19)
Pike of Judgement (w/ Restores +2 Health every 1 sec)

Wang Yi with her DLC weapon is an absolute monster. Those tiny piercers shouldn't have much reach but not only is she very mobile during her flow attacks which help with that, but for no reason her Stun Trigger has huge reach. A lot of her Flow attacks have grabs in them, which means that they can ignore enemies charging their Trigger attacks and make you invincible for the duration of the grab attack. Her Knock-Down Trigger is her absolute best tool, it starts with a grab and it's quite fast, which means you get invincibility and the ability to interrupt with a quick and simple button combination, abuse/spam the hell out of this. Her Special Attack is very good against all kinds of crowds, human and animal alike. Her ground Musou is very good (dat laugh), but I found her Air Musou to be quite weak.

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I pick Gem elements based on the character's Musou and Special attacks.

Why not Musou difficulty? Because it's just a grind fest, not actually difficult. You also get the same experience rewards as Ultimate.