The sword had a sharp blade made of ice. In your attempted stabbing, it shattered.
The next user is travelling through a portal, when the portal closes, with half of their body in one location, and the other half elsewhere.
I have a portal gun, and I shoot a portal at half of my body, and shoot another under the other half.
The next user is banished to the Far Lands (look it up on the Minecraft Wiki).
/gamemode 1
The next user's blood turns into lava.
...Right when i finished bleeding to death.
The next user is sticking a fork in the toaster at the same time as sticking thier OTHER finger in the electrical outlet.
Turns out, it was a real life Basilisk lizard, which is harmless.
The next user is subjected to a gravitational field strong enough to tear their body apart.