What was the biggest contract in NFL history?

Answer 1

As far as total dollars go, it was the 10 year, $130 million contract extension that Michael Vick signed with the Atlanta Falcons in December, 2004.

That contract was voided when Vick was convicted of running a dogfighting operation in 2007.

Answer 2

Dwight Freeney signed a 6 year 72 million dollar contract.

Answer 3

Mike Krzyzewski has a "lifetime" contract.

He has the option to coach for duration of his choosing.