RoXXon and Secret Empire engineered him with heightened strength, speed, agility, endurance, reflexes, senses, and superhumanly strong jaw muscles aiding canines filled with chemical foam that can paralyze and kill people with a bite
Baxter, like his ex-wife Hellcat, was first published in the 1940's in "Archie and Veronica" style teen comics. He debuted in Miss America Magazine #2. The above listed first appearance is for when Baxter was adapted into the main Marvel Universe. He became Mad-Dog in Defenders (1st series) #125.