Wait does it have to be real people? I got some serious badass movie characters in mind...
Tony Montana first of all. Went from working in a little sandwich shop to becoming a major player in the drug business. Plus he fu**ed some serious sh*t up with his M4 w/ attached Grenade Launcher.
Jimmy Conway (Robert De Niro) and Tommy DeVito (Joe Pesci) from Goodfellas. The mafia at its finest, plus its based closely on a true story.
Here's a clip of Jimmy and Tommy killing Billy Batts, a made man. http://www.youtube.com/watch?v=igHuG0HWVf4
Sonny Corleone from the Godfather, played by James Caan. A ruthless mob boss, had the mafia underworld in fear, unfortunately he was taken out before he could wreak any more havoc in NYC.
And lastly, Nicky Santoro from Casino. Casino is another movie based closely on a true story. Nicky Santoro, played by Joe Pesci is Robert De Niro's muscle in the Casino business in Nevada. When a man insults De Niro, Pesci fu**s him up bad in this clip: http://www.youtube.com/watch?v=iELKMNjZx9o
Oh and yes, the guy who is talking to Pesci in the Casino clip is the same guy that plays Billy Batts in Goodfellas.