The Carcass is the third boss in Cry of Fear, being fought at the end of chapter three on the rooftops. Carcass is a bloated piece of rotten meat stuck to a chair held in the air by several chains that hover above him. He appears to be a symbol of Simon's grief - primarily in regards to Sophie herself, connecting Sophie's eventual fate in the ending heavily to the creatures own. Its design also implies connection to Simon's crippled state, as it is confined to a chair and unable to move without the aid of the chains.
His attacks are similar to two creatures from Afraid of Monsters: Director's Cut, the Bleeding Specter and secondarily the Launcher Ghost, in which he fires ghostly projectiles towards the player that track his movements and are difficult to dodge. Due to the difficulty in avoiding his attacks and the high amount of damage it causes, Carcass can be a very lethal foe for players who are inexperienced in fighting him. Once killed, Carcass falls limp in his chair and the chains lose their flight, the creature and its chair falling to the ground below and vanishing.
For those who do not wish to fight him, it is possible to flee through a nearby window and cause Carcass to simply vanish. Though whether or not Simon chooses to kill Carcass is tied into what ending they receive regarding Sophie - if Carcass is spared, then Simon's guilt and depression associated with her continues to fester until he spitefully or possessively murders her in two of the four endings. The other two are achieved by killing Carcass, which will cause Simon to find peace with Sophie.
It is also possible the monster represents Simon, and his disability to walk since the creature sits in a chair, has no feet, and cant walk. Simon mentions that he feels he's just a sitting piece of meat in a chair. In which case, could represent the meaning of this monster, as if the chains represent how Simon feels he is "tied down" because he cannot walk, maybe that could be why if you kill the Carcass, you finally find peace with Sophie and accept your problem.