Even Butkus' peers were fearful. As Los Angeles Rams legend Deacon Jones said, "Roses are red, violets are blue, if you have any sense, you'll keep Butkus away from you."
"Concrete" Chuck Bednarik
The last of the 60-minute men in the NFL, Bednarik played angry -- "this is the way you go after them ... you're frothing from the mouth, and you say 'get him!' 'get him!'" Bednarik -- who played both center and linebacker -- passionately carries a torch for the old-school NFLer, holding contempt for the situational player in the modern game.
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Dobler once got in a casket just to feel how comfortable it was. The verdict? The former St. Louis Cardinals offensive lineman -- who developed a reputation as the meanest man in football -- liked it.
Jack "The Assassin" Tatum
At the center of the renegade aura that surrounded the Oakland Raiders of the 1970s was Tatum, whose severe hits are the stuff of legend.
Out to deliver a crushing hit and follow it with mean words, Lambert (nicknamed "Count Dracula in Cleats") was an intimidating force on a "Steel Curtain" defensive unit that helped fuel a run of four Super Bowl wins in six seasons for the Pittsburgh Steelers.
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"Mean" Joe Greene
Greene was the cornerstone of the Pittsburgh Steelers' turnaround from laughingstock to the dynasty of the 1970s. While transforming the fortunes of his team, Greene developed a reputation for having a temper and being a tad bit on the uncontrollable side on the field.
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Jones was an absolute terror on the field, and his gift for gab has entertained -- and, to some degree, enlightened -- football fans in the years since his retirement: "I'd made up my mind that I wasn't taking any prisoners and the wounded would be shot."
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Dick "Night Train" Lane
Clothesline and facemask tackles were outlawed in large part because of Lane, who is arguably the hardest-hitting cornerback in NFL history.
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Nitschke -- the ferocious anchor of Vince Lombardi's talented defense -- was described by Green Bay Packers teammate Jerry Kramer as a "junkyard dog."
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While developing a nasty reputation for logging penalties and fines for taking contact on the field to levels outside the rulebook, Harrison also managed to pull off one of the greatest plays in Super Bowl history.
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Suh's style of play earned him dirtiest player in the NFL honors -- as voted on by his peers. Two nationally televised incidents on Thanksgiving Day haven't helped discredit that notoriety, the first came against the Green Bay Packers in 2011, and again in 2012 against the Houston Texans.
The mythology of the leather-helmet era in pro football is often personified by Nagurski, who starred on both sides of the ball as a romping-stomping fullback and bone-crushing linebacker for a Chicago Bears outfit earning its distinction as the "Monsters of the Midway."
In the midst of an epic run of winning five NFL championships in seven seasons with the Green Bay Packers in the 1960s, Lombardi's fierce sideline intensity was well-documented by the fine folks at NFL Films ("What the hell is going on out here?!?").
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Known for his furious scowl, Cowher's sideline rage was highlighted during a "Monday Night Football" game against the Jacksonville Jaguars in 1997 when he nearly tackled Chris Hudson after a blocked field goal cost the Pittsburgh Steelers a victory.
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Mora's "playoffs?!?" rant following a heartbreaking loss during the 2001 season with the Indianapolis Colts will be relived forever (or, at least as long as sporting champions are determined through a playoff system).
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Follow a rather disturbing "Monday Night Football" loss to the Chicago Bears, Green -- then head coach of the Arizona Cardinals -- went on a memorable postgame tirade. You should watch it.