The Terminators.

Give myself and 'er indoors any kind of plant and we will kill it stone dead. Without mercy.
Over time, friends and family have become aware of our savage ways and have started giving us cacti and the most rare of orchids that can survive long periods of time without water, but it is futile.
This one lasted longer than most, but that's only because we wanted to torture it first. For three hours every day I would lock it in the airing cupboard with a CD of Chas & Dave playing at top volume.
Worked a treat. The fucker didn't stand a chance.