What are some of the most toxic flowers known to man?

Any plant of the Aconitum genus, such as Aconitum napellus. These plants are commonly known as Monkshood, Wolfsbane, or Aconite.

Lilly of the Valley, Convallaria majalis

Atropa belladonna, also known as Belladonna, Deadly Nightshade

Any Datura or Brugmansia species

Any species in the genus Digitalis, commonly known as Foxglove

Those are some of the most poisonous plants in the world, though Aconitum is by far the most toxic in the list

Nightshade, deaths-cap mushroom, potato greens, potato eyes, raw kidney beans, Try Googling poison plants

Wow nobody named oleanders, or euphorbias.

Clematis, foxglove, forget-me-nots, death camas, and lots of others. If you need more help, feel free to email me. Hope that helps!