Page "Grimlock" Paragraph 34

In his private thoughts, however, Grimlock considered Optimus Prime too weak to lead, seeking the position for himself.

When Soundwave read his mind and learned of this animosity, Megatron was able to trick Grimlock and the Dinobots into switching sides, attacking and capturing Optimus Prime.

To stop the turncoat Dinobots, two new ones were created: Snarl and Swoop.

Ultimately, it was when Optimus Prime threw himself into harm's way to save Grimlock from an explosion that he accepted his mistake and rejoined the Autobots.

In a rare display of modesty and humility, Grimlock emotionally apologised to Prime, admitted his jealousy of the leader, and accepted fault for the battle.

The two subsequently patched up their differences.