I believe you made a grave error in the distance between you and me; there's too little of it.
Smilodon were not known for their incredible speed...
Over long distances.
As an ambush predator, Smilodon, such as Argent Fatalis, have incredible acceleration and pouncing ability; able to hurtle toward a target before it can even dare attempt to react, particularly those unaware of the predator's presence. At absolute best and across the shortest distance, the human body can attempt to send nerve impulses at around one-hundred-twenty meters per second.
What's the actual average reaction time for a human being from the moment of input to physical reaction?
Slower than Argent's pounce.
This lovely piece, all about a massive feline in motion, was produced by the talents of Maquenda; she has an incredibly fast turn around provided she gets active input from the commissioner, and the quality of her work? I believe it speaks for itself, but I'll say it too.