Kincaid was first seen been let loose from a mental institution under suspicion of killing several children. While Spawn was human he was hired to kill Kincaid, but he was arrested before he could. Once freed he goes back to kidnapping and killing children uses his ice cream truck. Before Spawn could get to him he had already killed two kids. He hung his corpse in the offices of Twitch Williams and Sam Burke. He left a note on his body saying "Boys screamed and girls screamed. So I made him scream and scream and scream...". This was the cause of Sam and Twitch losing their jobs.
In Hell he meets Vindicator and Malebolgia and became a Hellspawn in his service. He was later killed easily by Spawn when he returned to hell.
Kincaid reappeared as a ghost possessing people and causing them to act out their violent impulses. Kincaid damns the souls of the people he coerces and gets stronger. Spawn, Sam, Twitch and Cogliostro investigate Kincaid's murder's but are unable to stop him since he can move from body to body. Spawn defeats him when he gets Kincaid to possess a cop and lures him to the "Dead Zone" which is an area of the city where Heaven is in control and Hell is weakened. Spawn and Kincaid fight hand-to-hand as they are both weakened, but he was killed by Twitch who shot him in the head killing the officer and Kincaid.
Kincaid came back again and battled the Spawn Christopher and ran a toy shop full of Spawn toys. They fought at a carnival that was actually a portal to Hell. He burns Christopher's eyes out by making him watch all his murders. However Christopher then kills Kincaid by tearing him apart with his suit.
Todd McFarlane's Spawn
Billy Kincain appeared in the HBO Miniseries, he was voiced by Ronny Cox. He's the son of the senator Scott McMillan, Billy Kincaid had a terrible secret that his father kept covered up: Kincaid liked children. Not in the normal way however; Kincaid would take the children during his Ice Cream route and back home with him. Later, he’d dump their mutilated bodies in garbage bags into Rat City’s alleys.
Kincaid’s downfall came about when he took Wanda Blake’s child, Cyan. When Spawn heard this, he went after Kincaid to rescue Cyan. After a lengthy battle and nearly killing Kincaid, Spawn withheld and merely returned Cyan to her parents.
While Kincaid lay broken on the ground, Clown came up. Kincaid asked if he could have any ice cream and Clown replied “Sorry asshole, we’re all out of ice cream.” Clown then pulled out a gun and shot Billy in the head.