Kurotowa
Legend
Also worth noting, that the point of comparison for the two abilities including the knives in the touchstone Subclass, the Thief, is Fast Hands or Second-Story Work: if anything, the Soul Knife as presented is a bit OP, but is hasn't had the balance pass yet
Which is really a design flaw with Rogues as an entire class, isn't it? No subclass features between 3rd and 9th Level leaves very little budget for a really transformative subclass. At least, not until you've reached those higher tiers of play.