Devastator is an immensely powerful warrior, and in that sense the combination of the Constructicons into a merged being is a huge success. Mentally, on the other hand, he's very much less than the sum of his parts. Devastator's primitive psyche is limited to only the thoughts and actions on which all his components can agree, which results in raging bouts of destructive fury. Given the sheer power Devastator brings to these rages, Megatron has no complaints.

As an Action Master, he is partnered with Scorpulator.

Normally he is composed of the six robots...

However, in some realities, he goes from being a six-robot combiner to a five-bot one, Hook and Mixmaster being replaced by Hightower. In another, he was temporarily rebuilt with a modular design that allows Hook to replace Scrapper as the right leg, and any robot built with a compatible design to form the head, including Prowl and Megatron. This configuration was later abandoned in favor of having Scoop serve as Devastator's new leg, returning the other Constructicons to their original positions. In another timeline, Devastator became a Micromaster after his surviving components downsized into smaller bodies. In yet another timeline, Devastator is a female Transformer.

The ability to merge into Devastator was given to the Constructicons by Megatron around nine million years ago, not long after he brainwashed them into his loyal servants using the Robo-Smasher. Their former friend Omega Supreme learned of this new ability first-hand when the Constructicons combined in order to hold Omega fast, so that the Robo-Smasher could be turned loose on his mind. Omega overpowered Devastator, however, and tore himself free of the Robo-Smasher, left not subservient to Megatron, but with a burning desire for vengeance against the Constructicons. The Secret of Omega Supreme

Millions of years later, in 1984, having joined Megatron on Earth, the Constructicons were charged with tunnelling under Autobot Headmasters in order to destroy Teletraan I. Confronted by the Dinobots and forced back outside the volcano base, the Constructicons realized they were no match for their new opponents, and combined into Devastator to fight back—the first of several battles between the giant and the Dinobots that wound rage through the Transformers' time on Earth. The Dinobots fared poorly in their first meeting with Devastator, but before they fell, their fellow Autobots returned to lend them a hand. Hound distracted Devastator with a hologram of a giant Autobot, allowing Optimus Prime to blast him dead center, causing him to disengage into the separate Constructicons. 

When Megatron attempted to tap the Earth's core to give the Decepticons a limitless supply of geothermal energy, Devastator defended the project from Autobot attack. To get around the giant combiner, Chip Chase and Wheeljack created dominator disks which forced the Constructicons, and thus Devastator, into serving the Autobots. Unfortunately, Megatron had anticipated this plan and built a device to override the dominator disks. When he turned Devastator against the Autobots, Wheeljack turned up the power on the dominator discs, which only served to fry Devastator's logic circuits and sent him berserk, damaging the controls for Megatron's drill just as it was about to pierce the Earth's core. Working together, both factions restored Devastator to Megatron's control and sent him into the ground to take out the drill before it could destroy the Earth. Devastator was surprised by Megatron's cowardly absence after he returned surface, but merely believed Megatron left to plan their next attack. The Core 

Allying with Autobots Grapple and Hoist to construct a Solar Power Tower of Grapple's design that they could then steal for the Decepticons, the Constructicons formed Devastator to install the sun-harnessing sphere component on top of the tower. After the villains took control of the tower, the other Autobots arrived to stop their plan and were confronted by Devastator once again, but managed to fell him by tricking him into collapsing the tower right on top of himself. The Master Builders

Devastator got his first rematch with the Dinobots when the prehistoric anti-heroes attacked the Constructicons as they were unloading a supply of Cybertonium from the space bridge. Scavenger was caught off-guard by the Dinobots before he could join his team-mates in forming Devastator, and the one-armed giant was unable to prevent the Dinobots from transporting themselves to Cybertron. Devastator had pulled himself together by the time Spike and Carly arrived, hot on the Dinobots' trail, but Carly's superior driving skills allowed her to navigate around his stomping feet and make it into the bridge as well. Not one of Devastator's better days. Desertion of the Dinobots, Part 1 

Another rematch of a different kind was soon to come when the Constructicons crossed paths with Omega Supreme, but the Autobot titan's rage allowed him to quickly overcome Devastator, burying him beneath an avalanche. The Secret of Omega Supreme

After the Triple Changers temporarily disposed of Megatron and Starscream, the Constructicons threw in with Blitzwing as the new Decepticon leader, building a maze around his base of operations. Unsurprisingly, Blitzwing refused to uphold his part of the bargain and make the Constructicons his leadership partners, so the enraged team formed Devastator to improve their bargaining posture. Megatron soon returned and put Blitzwing and Astrotrain in their place, but Devastator did not fall in line so easily, and continued his attack against them all, forcing all the in-fighting Decepticons to team up to eventually take him down. Triple Takeover Betrayals remained the order of the day when Devastator next saw combat, called up by Megatron to deal with another plot by Starscream and his new troops, the Combaticons. Starscream had foreseen Devastator's involvement, however, and had given his Combaticons the power to combine into Bruticus, who soundly defeated the Constructicons' combined form.