Accomplishments.

He was most noted for the St Valentines day Massacre.
He was also on the FBI's most wanted but they never had enough evidence to arrest him.
St. Valentines Day Massacre was against a rival gang, that of George "Bugs" Moran's Northside gang.  Moran's gang was nowhere near as successful as Capone's.  They met in a building that would not raise any suspicions. The building was the main liquor headquarters of Moran's gang. Capone's crew were dressed as police so the rival gang thought it was a police raid. As a result, they dropped their guns and put their hands against the wall. Using two shotguns and two machine guns, the Capone men fired more than 150 bullets into the victims.  The man accused of the murders was Jack McGurn, one of Capone's paid henchmen, but Capone was never indicted for it.