To begin the fight quickly in all cases except Death Sword Skip with Jumpstrike, press B to pull the sword as soon as possible after entering the room and jump attack from where Link is standing, then skip the cutscene. Transform into wolf, turn on senses, approach Death Sword, wait until it swings its sword, and then finish the first phase of the fight by biting repeatedly with A or with 5 timed B attacks. To prevent the B attacks from missing Death Sword, space them so that the last 3 are part of a separate combo from the first 2. Note that it is possible to softlock by bonking into Death Sword's sword on the final B attack.
Death Sword's stun timer begins when it is hit for the first time, but the third part of a sword combo will reset its timer. Repeatedly resetting the timer makes it possible to finish the fight in one cycle. Note that the first and second slashes of a combo do not reset the timer, and finishing a 4-part combo will always end the timer.
Hit Death Sword with the Clawshot or Boomerang to make it fly around the room, then charge a spin attack. Release the spin attack when Death Sword is flying by to knock it to the ground. Swing the Ball & Chain to hit Death Sword 3 times, then chain together 3 sword slashes in a combo, but hesitate to avoid finishing the combo. Repeat this for a total of 3 3-part combos, then complete a full 4-part 4th combo to end the fight.
It is faster to hit Death Sword 4 or 5 times with the Ball & Chain before beginning sword combos, but this makes it more difficult to reset the timer with a 3-part sword combo before the timer runs out. This method is slower than skipping Death Sword.
The following "setup" by SVA is the fastest known way to kill Death Sword. The timings on this method are strict.
Hit Death Sword with the Clawshot or Boomerang to make it fly around the room, then charge a spin attack. Release the spin attack when Death Sword is flying by to knock it to the ground. Chain together 3 sword slashes in a combo, but hesitate to avoid finishing the combo. Repeat this for a total of 5 3-part combos, then complete a full 4-part 6th combo to end the fight. This is slower than using the Ball & Chain or skipping Death Sword.
Hit Death Sword with the Clawshot or Boomerang to make it fly around the room. Pull out and begin twirling the Ball & Chain while Death Sword moves around the room. When it flies close and gets hit, move a bit closer to it so the Ball & Chain will continue to hit it on the ground. Hit Death Sword with the Ball & Chain 5 times, then repeat the entire process once more to finish the fight. This is slower than skipping Death Sword and both methods of 1-cycling Death Sword.
With a precise wolf Super Jump, it is possible to skip the entire Death Sword fight. This saves about 15 seconds over the 1-cycle with Ball & Chain.
This is the standard method for performing DSS.
The video below shows a buffered version of the trick. Since the charge attack releases when the player stops holding B, pulling up the item wheel on a frame where Death Sword looks to be in a good position means that you can simply close the item wheel and let go of all inputs to release the charge attack. The item wheel frame in the video below is a good example of what a good Death Sword position looks like. However, since the camera and Link's position are unlikely to be consistent across multiple attempts at the trick, timing the superjump often requires judging Death Sword's position without its surroundings appearing exactly the same every time.
Here is a closeup on the frame the B attack is released in the video above:
Adding a slash in step 4 of the setup described above costs about 3 seconds but gives a little more time for adjusting the camera after transforming.
If Death Sword gets stuck flying in place after circling the room, it is still possible to get it to land and attempt the superjump.
It is possible to skip the fight before it has begun with a Jumpstrike LJA. This requires precise positioning and a fairly precise angle but has the following setup:
Death Sword has two conditions that cause it to fly away after being knocked to the ground, and only one of them has to be true for it to fly away.
The 1-cycle abuses the fact that the timer doesn't run down as long as Link is slashing his sword, regardless of whether he is hitting Death Sword or not.