U-555, known as Death Avenge (デスエベンジ Desu Ebenji) in Japan, is the sub-boss of Tidal Whale's stage in Mega Man X5. It is a giant, whale Mechaniloid that once belonged to the marine museum and was affected by the Sigma Virus. It will pursue the player throughout the stage three times, each time attacking with a different parts of its body. First with its head, which releases Dejira GR's and fires lasers from its mouth, then with its tail (that is equipped with four missile launchers), and finally the upper body, where its core is located.
- The Mega Mech Shark from Mega Man 9, and the Sea Canthller from Mega Man X2, are similar to this boss.
- The name U-555 may be based on the German submarine U-55.
|Mega Man X5|
|List of Mavericks|
| Crescent Grizzly (Grizzly Slash) • Tidal Whale (Duff McWhalen) • Volt Kraken (Squid Adler) • Shining Firefly (Izzy Glow)|
Dark Necrobat (Dark Dizzy) • Spiral Pegasus (The Skiver) • Burn Dinorex (Mattrex) • Spike Rosered (Axle the Red)
|Sigma Head • Magma Dragoon • Dynamo • Shadow Devil • Rangda Bangda W • Zero • Mega Man X • Sigma|
|Mega Man X's Special Weapons|
|C-Shot • Goo Shaver • Tri-Thunder • F-Laser • Dark Hold • Wing Spiral • Ground Fire • Spike Ball|
|Zero's Special Techniques|
|C-Sword • F-Splasher • E-Blade • C-Flasher • Dark Hold • W-Shredder • Quake Blazer • Twin Dream|
| - Mega Man X -|
Force Armor • Falcon Armor • Gaea Armor • Ultimate Armor
- Zero -
|Hunter Base • Zero Space|
|Walkthrough • Parts • List of Enemies • Eurasia • Enigma • Space Shuttle|
Damage Data Chart (X) • Damage Data Chart (Zero) • Game Script (X's story) • Game Script (Zero's story)