Unarmed vs. Knife

[Toptomcat]

Judo 18 + All-Out Defense (Parry) + Retreating Parry + Cross Parry, followed up by an Arm Lock, is a very attractive answer, providing a very reliable defense immediately followed by an attack that controls, damages, and takes the weapon out of the equation. Buy up Arm Lock and Counterattack to enhance it.

I'd choose a grappling answer over a striking-oriented one because you specify a single assailant and not more than one, where grappling becomes more problematic. I'd choose a reactive answer over a proactive one because the after-a-parry application of Arm Lock permits the opponent only one chance to parry you rather than two, and giving them a chance to parry you risks hand injury per the B.376 rules for parrying unarmed attacks with edged weapons. I'd choose a retreating parry because duh. I'd choose a Cross Parry because I'm assuming my enemy doesn't have the high skill needed to Rapid Strike or the Extra Attack advantage.