Grounder

is a Badnik that first appeared in Sonic the Hedgehog 2. It is similar to Burrobot from the original Sonic the Hedgehog in terms of its design and attack pattern.

Sonic the Hedgehog 2
The Grounder Badnik made its first appearance in Sonic the Hedgehog 2. It appeared only in the Aquatic Ruin Zone.

Sonic the Hedgehog Pocket Adventure
Grounder later on made another appearance in the Aquatic Relix Zone in Sonic the Hedgehog Pocket Adventure.

Attack Pattern
Much like the Burrobots, the Grounder badniks mainly attack Sonic and Tails by breaking through walls and launching a surprise attack.

Adventures of Sonic the Hedgehog
In the television series Adventures of Sonic the Hedgehog one of the main antagonist of the show, Grounder, was based on the Grounder Badnik of the same name.

In this media, Grounder is one of the main henchmen of Doctor Ivo Robotnik. Together with Scratch he was created to be a part of the Super Special Sonic Search and Smash Squad, which job it is to eliminate Sonic the Hedgehog and aid his creator in his various schemes. Grounder, however is incredibly stupid and gullible, and often ends up causing his team and Robotnik more trouble when Sonic is trying to foil Robotnik's plans.

Sonic the Comic
In Sonic the Comic Grounder was a second-generation Badnik, created by Robotnik. The Grounder was designed as an upgraded version of the Burrobot. As well as its nose drill, it also has a drill at the end of each arm. It tends to hide behind walls and smashes through them when it detects a target on the other side.

Grounders were used sparingly by Doctor Ivo Robotnik throughout Sonic the Comic's run. During his initial reign over Mobius, they were only utilised on one occasion, helping Robotnik break into Doctor Ovi Kintobor's Laboratory along with his Squeeze Tag Machine and several Crawlton and Tunnelbot models. They succeeded in breaking into the Freedom Fighters' base, but were thwarted when Knuckles the Echidna arrived to help. The battle was taken outside where Knuckles, Sonic the Hedgehog and Johnny Lightfoot finished them off.

Trivia

 * It should be noted that Grounder is one of the few badniks in Sonic the Hedgehog 2 that features the Eggman Empire symbol, which can be seen on its shoulder armor.