Sinnertwin is one of the five Terrorcons that combine to form Abominus. He is a Decepticon with the role of Sentry. Besides forming an arm or leg of Abominus, Sinnertwin also transforms between his robot mode and his beast mode. He is constantly looking for some trouble in which he can involve himself, but there is one thing that does bother him and that is small creatures such as mice, insects and mini-droids (according to his Tech Spec).

The Generation 1 Sinnertwin was released in 1987. He was also available in the Abominus gift set released in Japan in the same year.