The Combaticons were a gestalt team of Decepticons added to the Transformers toy line in 1986. While they went on sale at about the same time as the Aerialbots and Stunticons, they weren't added to the Transformers cartoon until sometime later. The team consisted of Swindle, Brawl, Vortex, Blast Off, and their leader Onslaught, and combined together to form the super-robot Bruticus.
The Combaticon team was introduced in the cartoon episode "Starscream's Brigade", created by Starscream from old abandoned military vehicles and imbued with personalities stolen from a "prison" of disembodied criminal personalities on Cybertron. They are successful in attacking Megatron and the Constructicons, defeating them as Bruticus, only to get stomped from behind by Menasor and exiled. They return to Earth in the next episode "The Revenge of Bruticus" and are eventually brought under control and enlisted with the rest of the Decepticons. They appeared again from time to time throughout the rest of the American cartoon series.
The Combaticons' Autobot counterparts were the Protectobots, although that team never got as much airtime in the cartoon. By this time there were enough gestalts and large Transformers (like Omega Supreme) that they could fight each other more or less interchangably.