Cappy, Super Mario Odyssey's cute companion character, can accidentally kill off the game's hero.
It's not on purpose (probably), but it can be done. Twitter user DefinitivNichtSacha posted video footage - embedded below - last night of how to do it.
First off, you'll need to Capture a Piranha Plant enemy - such as this one here in the Luncheon Kingdom. You'll need to feed it a rock first. After that, you can command Cappy to attack the plant, killing it and Mario himself.
With the plant gone, there's no more Mario. You'll have to reload a checkpoint to ensure he's reincarnated.
The whole episode brings to question the exact mechanics of the Capture method. Where does Mario's body go when he possesses something else? It's probably best not to think about it too much.
Nintendo has yet to mention the issue - presumably it will be patched in a future update.