AARRRRRRGGGGGGGGGHHH! 
ok.
It was two footed - both feet, off the ground, doesn't matter if it was done with murderous intent or Gerrard just wanted to stroke Carricks shins with his pinky-toes to make them feel less sore. Once both Gerrard's feet left the ground in a lunging challenge type fashion it became a clear, unambiguous red card offence.
Same way as the intent behind a professional foul or an elbow to the face doesn't matter either.
You like quoting the law, so let me quote it for you.
"Any player who lunges at an opponent in challenging for the ball from the
front, from the side or from behind using one or both legs, with EXCESSIVE force
and endangering the safety of an opponent is guilty of serious foul play."
Let's look at definitions:
“Careless” means that the player has shown a lack of attention or
consideration when making a challenge or that he acted without precaution.
• No further disciplinary sanction is needed if a foul is judged to be careless
“Reckless” means that the player has acted with complete disregard to the
danger to, or consequences for, his opponent.
• A player who plays in a reckless manner must be cautioned
“Using excessive force” means that the player has far exceeded the necessary
use of force and is in danger of injuring his opponent.
• A player who uses excessive force must be sent off
So as you can see the intent does matter.
