The worst invasive plant species I've had to remove has so far been alien creeping thistle (Cirsium arvense). This thistle species is perennial and it easily propagates itself vegetatively if you happen to break the roots while weeding it. The plant is also covered in irritating spines that have pierced through my calf skin gloves way more than on one occasion.
In spite of this plant's invasive qualities, I have been reading the in the past year that this weed may still be valuable as an emergency famine food. I have so far only found two guides on how to render the plant safe for human consumption: one in a comment left by a reader in the guide for this plant on PFAF and another in a PDF that I discovered just an hour ago. Both guides recommend pulverizing the leaves in a blender thoroughly to break down the outer leaf spines after boiling the leaves down. I recommend archiving the PDF in case the hyperlink below rots soon after I post it.
Mandrake...takes on and holds the influence
of the devil more than other herbs because of its similarity
to a human. Whence, also, a person’s desires, whether good
or evil, are stirred up through it...
-Hildegard of Bingen, Physica