Anti-Riku

The AntiRiku (アンチリク) is a slightly weaker, Heartless version of Riku that is found in Kingdom Hearts 358/2 Days. It appears as a secret boss in Mission 93, replacing Riku at The World That Never Was.

Strategy
AntiRiku uses the same battle techniques as the true Riku. At the start of this battle, immediately Lock-On to the boss. This should aid you in keeping track of him, as Riku is fast. As soon as this is done, begin hammering AntiRiku with a strong combo. You will not be able to deal the finishing blows in some of your combos, as the boss will utilize Dark Shield and block them. A majority of this battle will be following this AntiRiku around the battlefield in front of Memory's Skyscraper.

When you get close to AntiRiku, he will attempt a series of thrusts with the dark Oblivion Keyblade it wields. AntiRiku may also launch a Dark Firaga attack if the player is not within close range. When AntiRiku's HP starts to diminish, he will begin to utilize a Dark Break-style desperation attack. This can be dodged via the Glide ability or if the player can start a fast run. Just when AntiRiku's HP is about to hit zero, he gains access to his Limit Break, Darkstrom. AntiRiku will jet around the battle area, unleashing columns of black flame at the combo's end. You can time this attack to when the boss's weapon begins to glow with a white-blue energy.

So long as the player follows this strategy, AntiRiku shouldn't be a problem to defeat. Keep in mind that since this boss is only battled in Mission Mode, the characters you choose to play as will have various effects on this battle.

Trivia

 * Like the real Riku, AntiRiku is fought to the battle theme in "Another side, Another story..."
 * AntiRiku 's Dark Shield was a Reaction Command in Kingdom Hearts II.