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This is a list of bosses found in the Metal Slug game series. They are enormous and powerfull baddies that ahve advanced attacks
- Tetsuyuki (inprovised fortification constructed from a crashed Type 770 Takatsu-class aerial gunboat/bomber)
- Hairbuster Riberts (Prototype rebellion Heavy Bomber)
- Tani Oh (Giant self-propelled artillery armed with andro cannons)
- Shoe & Karn (Cooperative mission tanks designed to cover each other's backs, acting in tandem)
- Iron Nokana ( Multi-role combat vehicle designed primarily to hold up large troop movements)
- Hi-Do (Second generation attack helicopter built specifically for Donald Morden)
- The Keesi (VTOL heavy bomber/"The Keesi II", a combined bomber and troop transport)
- Aeshi Nero [also known as Assy Nero] (Giant subterranean excavator, basically a huge robot snake with a hypercharged andro cannon in it's mouth)
- Dragon Nosuke (Platformed urban tank used to defend vulnerable trains with a variety of weaponry)
- Big Shiee ("Amphibious vehicle of destruction", basically a naval destroyer on tracks)
- Hozmi (Covert operation submarine built by the rebels using supplied martian technology)
- Dai-Manji (UFO armed with energy bombs and an electric beam projector)
- Rugname (Martian mothership which has an underside port for a Dai-Manji to dock onto, hypercharging it's electric beam into a lethal laser)
- Huge Hermit (a giant hermit crab whose current shell used to be a large tank)
- The Ten Commandments Of Moses [also known as Monoeye UFO] (Alien artifact used by the Martians for a first strike, which defends itself by starting off a zombie plague among people near it)
- Jupiter King (Giant nuclear-powered robot which defends the rebels' underwater weapons factory)
- Sol Dae Rokker (Japanese sun god's instrument, which in truth is a martian weapon)
- Rootmars (leader of the mars people, who looks like a huge martian with an exposed brain)
- Bura Gariae [also know as Brave Guerrier] (Amadeus blimp "Bura Gariae")
- Toschka Dalanue (Pillbox tower "Toshka Dalanue")
- The Iron (Improved multi-role combat vehicle "Iron")
- Big John (Giant machine doll converted by the Amadeus syndicate to carry zombie and mummy plagues)
- Sea Satan (Submarine "Sea Satan")
- Amadeus [also known as the Doctor] (Mad scientist who leads the Amadeus syndicate)
- Metal Rear (Ptolemaic Ultra-giant Metal Slug: Unit #04 "Metal Rear")
- Secret Weapon of The Luftwafe [also known as Shooting Ray] (Ptolemaic Large-sized aerial aircraft carrier: Unit #02 "Secret Weapon of The Luftwafe")
- Wall Crawler (Ptolemaic special unit: Unit #01 "Wall Crawler")
- Sand Marine (Ptolemaic amphibious assault landing ship: Unit #02 "Sand Marine")
- Evil Spirit Incanate [also known as Scyther] (a giant scythe-wielding demon)
- Bull Drill (Giant rebel drilling machine)
- Iron Sentinel [also known as Iron Slider] (Missile Panzer Tank "Iron Sentinel". General Morden rides it by himself.)
- Brain Robot (A large robot controlled by an atificail brain. It's on the same side as the Invader.)
- Elder Centipede [also known as Sea Worm]
- Invader Queen [also known as Venusian Queen]
- Worm Mecha
- Crablops [also known as Crab Mecha]
- Fall Mecha
- The Union
- Rebel Gigant
- Kraken (Giant robot octopus from the future)
- Formor (Rebel version of the metal slug tanks, twice as big and has same weapons)
- Emain Macha [also known as the Twins]
- Kaladgolg (Basically the Tani Oh on a railway flatcar and not a giant tank)
- The Keesi III
- Cabracan