Joseph Martello (Earth-4678)

Joseph Martello, also know as Hammerhead, is one of the most influential leaders of the Maggia, one of the oldest mafia organizations in New York City. During his life as crimelord, he came up against all sorts of opponents, such as the NYPD, the masked superhero Spider-Man, and even against the media, with J. Jonah Jameson during the 1980s. During his youth, he was nearly beaten to death, but a surgeon saved his life by inserting a steel plate in his skull, more precisely on his forehead. This gave him his trademark square-shaped skull, attaining the moniker Hammerhead. The incident also left mental sequelae in Joseph, who became a homicidal maniac afterwards.

Source

 * https://marvel.fandom.com/wiki/Joseph_Martello_(Earth-1048)