Pretender Grimlock is one of those he displays to the Autobots. He is identified as a Decepticon.

Was Grimlock ever a Decepticon?

Grimlock is a Decepticon-turned-Autobot Dinobot from the Aligned continuity family. ... Grimlock is a wild card among the Autobots. Huge and powerful, he's also headstrong and reckless.

Are Dinobots Decepticons?

The Dinobots are an Autobot subgroup from the Generation 1 continuity family. In some continuities, before they arrive on Earth, they are known as the Dynobots. ... Few Autobots are closer. As so many battered, bruised and beaten Decepticons can attest, if you confront one Dinobot, you confront them all.