Sludge is the odd bot out of the Dinobots. Despite his various appearances in continuities, Sludge is actually described as being a gentle giant when not in battle. Though apparently not as friendly as his fellow Dinobot Swoop, Sludge is a lot nicer than the other three Dinobots; Grimlock, Slag, and Snarl. One example of this was in the UK Generation 1 comics when Sludge fell in love with a human named Joy Meadows. While Sludge may be the biggest Dinobot and the second most powerful, he is also considered to be the dumbest of the five. Grimlock himself has even called Sludge dumb. However, his intelligence varies upon continuity. In some versions, he is flat out stupid while in others he is simply simple minded or just less intelligent than the other Dinobots. Unlike the other Dinobots, Sludge dislikes Optimus' leadership because he believes that the strongest is the one who should lead. In his eyes, Grimlock is the strongest. Because of this, Sludge loyally follows Grimlock no matter what. Sludge's strength is seen in both his robot and his Brontosaurus mode. In his dinosaur mode, Sludge's stomps are so powerful they can shatter bridges with one step. Due to his durability and build, Sludge is especially ideal for battling in areas like jungles and swamps. Like the majority of his fellow Dinobots, Sludge is armed with an Energo-sword and a laser rifle. However, he is usually seen with just the rifle.
Though Sludge looks big and intimidating, he is gentle and shy. He is probably the second-nicest of the Dinobots (after Swoop), and is very loyal to Grimlock. He dislikes Optimus Prime's leadership, and believes that the strongest should lead, and see's Grimlock as the strongest and thinks he should be leader of the Autobots.
Powers and Abilities
Sludge is tremendously strong, and his great strength is second only to the likes of Grimlock, Optimus Prime and Megatron. A punch from him in his robot mode possesses enough force to shatter a suspension bridge, and a stomp from him in his dinosaur mode results in even greater damage and it could even crack open a mountain. His heavily armored hide is also nearly impervious, and can only be harmed by the most powerful sorts of attacks. He is a fearsome foe in battle, and is very good at fighting in swamps, jungles and water.
Transformers: Fall of Cybertron - Sludge appears in all versions of this game. He is a member of the Autobots and serves under Grimlock in the Lightning Strike team. While Grimlock is tasked with guarding a passage to the Ark he and the rest of his team, Swop included, left their post because Grimlock thought the Decepticons, especially Shockwave, was up to something and they went to the Sea of Rust to check it out. Optimus Prime dispatched Cliffjumper, Jazz, and Sideswipe to find the missing team so he could question why they left their post. They followed the trail to an ancient set of Cybertronian ruins that belonged to the astronomers who cataloged numerous worlds, including Earth. Grimlock and the rest of the team were captured by Shockwave, but Sludge was damaged to the point of stasis lock and left behind in the ruins for Cliffjumper to find. Cliffjumper used his audio logs to hear his "death". Sludge was never upgraded to his usual Brontosaurus alternate form. His death was remembered by Swoop who mentions to Grimlock that he never made it out of the ruins.
However, in the comic book sequel: Transformers Prime: Rage of the Dinobots; Sludge is seen in perfect health and equipped with his dinosaur alt-mode. How he came to survive his fate in Fall of Cybertron and acquire a dino-mode is yet to be explained.
Sludge is also the only Dinobot that isn't available for in Multiplayer mode, even as a DLC, but if he was he'd most likely be available for either the Titan class or the Destroyer class.