Mega-Shadow

The Mega-Shadow (メガシャドウ) is a Pureblood Heartless that is found in Kingdom Hearts 358/2 Days.

Kingdom Hearts 358/2 Days
These mid-sized Purebloods retain the attack patterns of their smaller cousins, but also use a dangerous tackle. Block it, and they're left wide open.

Strategy
At the start of the battle, Lock-On to the Mega-Shadow. Ignore its smaller brethren, as Xaldin will handle them while you attack the Boss. The Heartless will sink into the floor, rendering attacks useless. Once it resurfaces, start hammering the beast with the Keyblade. Use caution, as the Mega-Shadow may attempt to knock the player back with a slash attack. This is this Heartless Boss's only tactic.

All in all, this Boss Battle should be fairly simple, so long as the player utilizes Magic and doesn't keep too close. Use the Limit Break to finish the battle. Keep this strategy in mind for any further encounters with the Mega-Shadow in Beast's Castle or Twilight Town.

Worlds fought

 * Beast's Castle
 * Twilight Town

Trivia

 * In the first encounter with the Mega-Shadow, the battle music is "Tension Rising". In other appearances in Twilight Town, the battle theme is the normal "Sinister Sundowns".