Everyone knows this one, which is the problem.
The tardigrade arrives pre-packaged as a meme: indestructible, survives space, outlives us all. Almost all of that is a description of one specific trick, performed under one specific condition, and stated without the condition it stops being true.
Here is the trick. When its water goes, a tardigrade does not die and does not carry on. It pulls in its legs, folds into a barrel — a tun — and stops. Not slows: stops. Its metabolism drops away to nearly nothing, its cells fill with protective proteins that set into a glass-like solid, and in that state it is not really an organism at all. It is an object. Objects are hard to kill. You can freeze it, boil it briefly, expose it to vacuum, hit it with radiation that would sterilise anything living, and the object does not care, because there is nothing running to disrupt.
Add water and it swells, unfolds, and walks off on eight clawed legs with the unhurried confidence of something that has just been dead for a decade.
But the animal in the puddle — hydrated, active, going about its business — is about as tough as any other half-millimetre animal. Squash it and it squashes. The superpower is not endurance. It is the ability to stop being alive for a while, and to start again.
That is a stranger thing than invincibility, and nobody puts it on a T-shirt.