Inferno is a Predacon who works for Megatron. He was originally a Maximal protoform, reprogrammed into a Predacon when the Predacons intercepted his stasis pod. His beast form is a fire ant.
At first, Inferno believed his pod to be his "colony", and attacked the Predacons as well as the Maximals. After being blown to bits and repaired, Inferno recognized Megatron as his master and called him his queen, which annoyed Megatron.
Inferno took Scorponok's place as Megatron's second in command when Scorponok fell to his death in the lava pool. At the end of Season 2 (where most of the Predacons are seemingly killed), he was supposedly killed by an energon explosion, but although he was seemingly vaporized, he is shown to have survived in Season 3.
In the final episode of Season 3, Inferno was killed along with Quickstrike when Megatron (oblivious to their presence) used the weapons system of the Nemesis ship to shoot an energy wave at the village. His remains were later used by the protohumans in the final scene.