On servers such as 2B2T, to bedtrap someone, you need an alt account to killaura them, that's not very efficient and takes up a whole account.
What if, instead, there was a contraption you could make that would trap them for good?
Well, by golly, you're in luck!
With this schematic, not only will your prisoner die, but you can chose the way in which they do!
Drop them from the sky! Throw them down a hole!
Recreate a toilet and flush them down the bowl!
Send them into lava! Feed them to the void!
Send them to a pizzeria with animatronic toys!
And all of that, with the inexpensive price of 17 obsidian and a few redstone items!
Not only that, but this contraption is hackerproof.
Unless the victim has reach or flight, which 99% of servers have plugins against, they aren't escaping.
It also has pistons that retract 2 ticks after the other one extends, to make sure the player never loses their respawn.
This way, even with terrible lag, the player will stay captive definitively.
P.S. The trap can also be toggled.