Beta's features included more advanced homing missiles, laser cannon arms, and large spiked gauntlets used for charging attacks. Beta navigated with jets and a tail-like rudder, and employed an advanced tracking system in his head, taking the form of a single green camera "eye".
Beta's fighting capabilities granted him the ability to create rainbow-colored force fields, fire a spread of several (ranging from 2 to 10) guided missiles to chase down moving targets, and fire powerful energy blasts from great distances using its new cannons, which would explode on contact with the ground. He was also much more agile than its previous form, being able to dodge missiles at extreme speed (leaving afterimages in its wake), and even still, could also simply bat away missiles with its shield-like gauntlets.
Battle with the Underground
When Robotnik sent the E-Series into battle Beta was one of the hardest to beat, he was finally beaten when the team brought their weapons together to form the Ultimax Cannon.
Last ditch battle
Robotnik used the entire E-Series to kill the Underground, but the planned didn't work and Beta was part of the members of the team who did survive the EMP, and was placed back in storage.
He was revived in another form in the Sonic Adventure adaptation, then returned to normal.