Oddly enough, when Emirate Xaaron and the Wreckers planned Operation: Volcano, Macabre did not appear to be on their list of intended targets - possibly because he's just a small-time thug who is awed by the likes of Octane. Sadly for him, Octane and the other Decepticons also treat Macabre with little more than contempt, so he is constantly looking to prove himself to them.
This is why he really wants to kill Emirate Xaaron.
Marvel Comics continuity
Macabre was part of a Decepticon strikeforce that included the Insecticons, the Coneheads, Blitzwing and the aforementioned Octane. Acting on information recovered by Shrapnel, they believed that they would have the chance of assassinating Xaaron, the leader of the Autobot resistance on Cybertron. In reality, the information had been deliberately leaked and they were unwittingly walking into a trap.
When Megatron called off the attack, the Decepticons turned back for fear of disobeying the Slag Maker - all except Macabre, who was so driven by his desire to be remembered for something that he continued on the mission alone. He had the target in his sights when Impactor intervened, taking the shot meant for Xaaron.
Frustrated at being cheated of his kill, Macabre jumped to his feet to take another shot, all the time ranting about how much he was going to kill Xaaron. Unfortunately for him, the assembled Wreckers blew him into spare parts, and that was the last anyone saw of Macabre.
Apparently, his gutsy go getter attitude in Marvel earned him a promotion in IDW as he now commanded the Decepticon Squadron X, response to the Wreckers. Obviously the most insane member of an insane bunch, after all how else could he get away with being a bright pink psycho killer? Anyway, Pova was his final place, long believed to have been killed in an escape attempt by Impactor, it turned out he got executed by what appeared to be a seriously upgraded UPC reader.
- According to Dreadwind in his letters page, Macabre transformed into a "bat-winged air current glider". No wonder he had an inferiority complex.