How to make endermen die in one hit, without the use of fall damage?

I built Ilmango's Endermen XP farm and its really fast. But one problem with the design is that the Endermen aren't one hit kills, unlike other (slower and larger) designs, since it doesn't drop the Endermen from a high place (since the lower the spawning platform is the more Endermen) to get them to half a heart. They require around 2 - 3 hits with a Sharpness V diamond sword (other designs only need a punch).

So, how can I reduce the health of them without using fall damage. They seem to teleport out of suffocation traps (which are anyways too slow) so is there a method other than fall damage to get them to half a heart?

So far, there isn't anything else possible to kill Endermen in one hit rather than fall damage. It isn't possible. I tried to test these things out, but none of them worked.

However, this doesn't mean that there is no way to kill Enderman in one hit 100%. If nothing is confirmed, then there is no possible way to do something like this.

From the Minecraft Wiki:

It is possible (but expensive) to kill an enderman in one hit, by using a diamond sword with the Sharpness V Enchantment, while also having the Strength II Effect active, and landing a critical hit.

Since I got clarification that you are looking for a mob-grinder, what you need to do is build your enderman farm way out into the void off of any End island, then cover every surface with blocks that stop their teleportation, such as water or lava. The spawning platforms would then be at least 32 blocks above where the killing chamber is, as that is the distance of teleporting (24 blocks vertical but 32 has been reported). You can then use a regular diamond sword at that point, or a suffocator or mob jammer since they have nowhere else to go.