Like his fellow Terrorcons, Sinnertwin is a horrific insult to nature itself. Sinnertwin frequently patrols the Terrorcons' lair with the hope of finding anything unfortunate enough to be alive in his presence. Then comes the killing, and what with his multiple heads and sadistic nature, this is not something one would like to witness. Ironically, he's terrified of small creatures.
He has the most awesome name in Transformer history. No matter what Slayride says.
Sinnertwin can combine with his fellow Terrorcons to form Abominus.