You can KO non-boss enemies in Sifu without killing them, which means that the brawler can be completed without murdering any of the dozens of minions guarding its five bosses. Perhaps that's the 'true' way to beat Sifu, if you're not trying to be its villain. I'll never know, because in order to finish the game I used a cowardly trick that has no place in a gentler run, since it involves sticking swords in people's guts.
Something I like about Sifu is that it doesn't explain every detail of its fighting system, so if you don't want one of its little touches revealed to you, maybe go check out Natalie's comparison between the game and Sloclap's prior work, Absolver. Otherwise, here's what the trick is all about:
The best unlockable attack in Sifu, if you ask me, is the Charged Backfist. It lets you deliver a solid whack to the head of anyone in front of or behind you (without turning to look at them, of course, because you're a badass) and when wielding a bat weapon, it becomes an endlessly useful trip attack.
When you're holding a bladed weapon, however, Charged Backfist becomes something very different. Partially charging it results in an unexciting upward sweep, but if you fully charge it before releasing, you'll dash forward and run the blade through the torso of whomever you're aiming at, sacrificing the weapon in exchange for an instakill (it gets stuck in their torso).
You do have to land the strike cleanly to get the kill: It can be blocked or avoided, and the charge-up animation takes a couple seconds, which makes it tough to use in regular combat. (I discovered it by accident.) It also doesn't make much sense to give up your sword just to kill one regular enemy. The move is extremely useful in a few specific situations, though, so long as you don't mind that my favorite PS1 game, Bushido Blade, would call what you're doing a "damned path."
The trick is to hold onto a sword until you encounter one of Sifu's elite enemies. Some of them will talk to you before your duel begins, which normally doesn't matter, because if you get too close or throw a punch while they're yapping, they'll shut up and start fighting. However, they're happy to keep on casually monologuing if you stand a few feet away from them gripping your sword and grunting as you charge up an attack. Sure enough, it's possible to impale them mid-sentence, ending the fight before it starts.
The Charged Backfist blade skip is particularly useful for two elite enemy encounters near the boss chamber in the fourth level, in the caves. I also used it to get rid of the guard standing in front of the final boss's room. These aren't encounters you'll dread, necessarily, but you're so fragile in Sifu that losing your concentration for just a moment can result in a death, and the one thing you don't want to do just before the final boss is add any years to your character's age (Sifu's penalty for dying, which moves you closer to its 'game over' state). This move negates the possibility of that happening. It's also unlikely that you'll beat each boss on your first try, so you'll have to go through these enemies again and again. Instakilling them saves time.
Disappointingly, I don't think the one-hit kill works on Sifu's bosses themselves. I tried it on Kuroki, the Japanese museum owner whose level introduces bladed weapons to the game, and she avoided the attack every time. I suspect that Sloclap knew we'd try our luck and included a hard rule that bosses always avoid the attack, although I haven't rigorously tested that theory.
Sifu will likely become popular with a few speedrunners, because it's challenging, not randomized, and I have a feeling that quite a few more tricks are waiting to be discovered—even after beating it, I haven't even tried all of its moves. For general tips, check out my guide to beating Sifu.
I also discovered a tactic I call "moneybagging" (let's ignore that there are probably 10 different dirty definitions for that) which requires the Environmental Mastery skill and only works in one spot in the first level and actually slows down your playthrough quite a bit:
