Shockwave

Shockwave is one of the Decepticons that was left to watch Cybertron by Megatron long ago.

In Dark of the Moon
Shockwave and his pet Driller attacked the Autobots when they were summoned to Chernobyl by the Decepticon agent Alexi Voskhod. This was done as an act of misdirection to ensure that the Autobots did not realize that the Decepticons actually wanted them to find the fuel cell from the Ark located within the facility. After Optimus retrieved the fuel cell from the Driller, Shockwave emerged from it to reveal himself to Optimus, and the pair quickly retreated underground, leaving Optimus very disturbed to see Shockwave on Earth.

Later, Shockwave took part in the invasion of Chicago. He and the Driller emerged from beneath the convoy of Autobots, and the Driller separated Optimus from his trailer. Shockwave left the Driller and proceeded to track down the Autobots. The Wreckers were sent to distract him, peppering his armor with fire from their machine-guns. He used a car as a shield and fired at them, and once they drove off, he menacingly began to pursue them down the road, missing the two small Autobots, Wheelie and Brains, who quickly fled.

Later, he noticed humans inside a building, and sent his Driller into the fray to topple a building and kill Sam Witwicky, Carly Spencer, Robert Epps, and the other humans inside. The beast was killed by Optimus Prime using his flight gear, however, and Shockwave, enraged by the death of his pet, opened fire on the Autobot leader, briefly disabling him and taking him out of the fight.

He soon joined Soundwave and Barricade in rounding up the other Autobots. Brains and Wheelie forestalled the Decepticons from further executing their prisoners by taking control of a Decepticon gunship, and dropping fighters onto the battlefield. Shockwave retreated further away with Barricade and some other Decepticons, but the human soldiers had set a trap and fired upon them. Shockwave was blinded by one of their parachutes, and his eye was then shot out by the Wreckers, causing it to dangle by its wires. His hose and gun backpack were damaged, as well. Optimus Prime then came charging back into the battle, and when Shockwave fired at him, the Autobot dodged the shot, donned a set of knuckle-spikes, and punched Shockwave so hard that part of his abdomen shattered. Even this did not put Shockwave down, but Prime did not let up - he punched Shockwave again, pinned the Decepticon down and tore his dangling eye out through his throat, finally ending the Decepticon's life. Optimus then used Shockwave's cannon to shoot out the control pillar set up in the city.

Trivia

 * Shockwave will become Thomas and Twilight's enemy in Thomas and Twilight Sparkle's Adventures of Transformers Dark of the Moon.
 * Shockwave returned in Thomas and Twilight's Adventure with Jimmy Neutron: Boy Genius, Brian Griffin vs. The Mummy: Tomb of the Dragon Emperor and The Wrath of Galvatrain and he plots to get revenge on our heroes.