At some point in the recent past, a battle happened between Sonic the Hedgehog and Dr. Eggman. This time, Eggman was piloting the Egg Viper mech, but Sonic defeated the villain. (StH: #1)
The Egg Viper was based on the machine of the same name in the Sonic the Hedgehog video game series, where it first appeared in Sonic Adventure as the final boss of Sonic's story. It was unnamed in the comic, but is considered tier 2 canon by this site's canon policy, as it does not contradict already established canon from tier 1.