Call it shamelessness, but in a battle to the death, one ought to use every means necessary to emerge as the one alive.
Kent knew that, and so he went for the only play in the book that has no counter: the Ball Buster.
Seeing his death two seconds into the future and making sure it never came to pass was a wake-up call to tell Kent that the Crimson Blood Demon General wasn't an opponent he could defeat using normal means.
Luckily, this mission wasn't to test who was the better swordsman. The quest wanted him to kill the poor bastard, and so he would just do that. Bursting his balls was basically his way of paying back the demon for cutting his arm off.
Also, he made this decision simply to invoke the wrath of the Crimson Blood Demon General. This way, he would unleash his true power, something that Kent needed to see so he could create a good killing move.
