Swamp Thing (Painkiller game series)

Swamp Thing is the second general of the Hell Forces, bound to attack Heaven. He is smaller than the Necrogiant, but uses his surroundings to his advantage. Daniel fights it in a swamp with corrosive waters. The creature is composed of water which makes it invulnerable to damage. It is possible to be turned solid in which state it becomes susceptible to attack. It attacks by shooting exploding bubbles, directing harmful fireflies or making wormlike water constructs. The way to damage it before it turns solid is to attack the glowing bubbles with the Shotgun while he walks over them. It is also possible to shoot the bubble he launches right as it flies out to damage him as well. After you damage him with some of the bubbles, he will turn vulnerable for a short period. After that, he goes back into invulnerability and summons 6 bubbles that don't glow. Shoot all 6 to make him vulnerable again. Use your Golden Cards at this point (Hopefully Double Haste and Rage are in there) and unload like mad. You should manage to kill him before he goes back into invulnerability. Overall, this boss is incredibly easy once you get the hang of what you are supposed to do, and its easy to beat him under 4:00 to get the very useful Dexterity card.

Trivia

 * The creature is likely a tribute to Man-Thing or Swamp thing from comics.
 * It is unknown whether the creature is a demon or a hellish creation like the Necrogiant.