Was there a need to be that harsh with the poor Smilodon?
Isn't that what one would ask if they saw that scene?
But what would happen to you when you are caught by one of those smilodons?
They would eat you alive—your limbs, organs, innards, and your blood—and you would be able to get a view of everything before you die.
Alex just wanted the smilodons to know how it felt, so he made them feel it.
Yes, his personal feelings did make him do it; the rage of the last betrayal and the frustration of being forced to run away were still there.
This smilodon became an outlet for every such negative emotion.
But that was not the only reason for Alex to do what he did.
When one is enraged, one's rational thinking gets clouded; Alex wanted to do just that.
He wanted to anger the smilodons.
Alex didn't know the number of smilodons, and he didn't know how many level 10 beasts were among them.