Sponsored by ABC’s new drama Red Widow: Organized crime has always thrived on intimidation and brutal acts, but sometimes the violence is unspeakably gruesome. Here are some of the most notorious mob hits, from a gruesome payback to the stool pigeon who couldn’t fly: Al Capone had an alibi for the massacre THE ST. VALENTINE’S DAY MASSACRE: Considered the “most infamous of all gangland slayings in America,” seven men were lined up against a…