Exarchon

Exarchon was the leader of the Threefold Spark presumably during the eponymous War of the Threefold Spark. Apparently he should not have been trusted.

You can't see me!

_{This character has no official visual representation in any Transformers product or media... yet, at least.}

Fiction

2019 IDW continuity

When Senator Orion Pax wondered whether he could still trust Megatron, Codexa claimed Cybertron once trusted Exarchon. Orion then claimed that Megatron was nothing like him.