Aconite is very poisonous. Every part of this plant is deadly. The poison starts working very fast; After two minutes you start sweating cold sweat, after which you get it very hot over your whole body. Then your mouth and throat start burning, after which you get very cold again. deadly cold. You get a foltering pain in your head, neck and back and you can even get blind. After that, it is over within three to four hours. Then you are dead. (So actually Aconite isn't a really good option to get rid of annoying husbands, since it isn't very unnoticable...)
If Absinthe is used in a too high doses, it can have a fatal effect. First there will come paralysis effects. For even higher doses, there can be effects like vomiting, tremors, kidney damage, hallucination, brain damage, coma and eventually death.
Deadly nightshade is quite poisonous and eating any part of it, though especially the berries, can result in death. When one is poisoned by the Devil's cherries, they first become very cheerful and chatty and will likely start singing or dancing. Though that might sound nice, the things that happen after that are absolutely bad. Because next, the person will get in a state of confusion and they will lose the ability to speak. Then, they will fall into complete madness and it is said that one can demand anything and they will do it. That is already pretty serious bad stuff, but there is even more! The next stadium will be one of mania and delirium, often ending with spams after which the poisoned person will fall asleep. It happens that people die in this proces. They sometimes choke.
Foxglove is extremely poisonous. Two leafs can already be deadly. It slows down the heart rate and therefore it has a paralysing effect. This can be very extreme, resulting in death.
Common ivy is poisonous. The hederine has a haemolytic effect, meaning that it can destroy red blood cells. And it can also cause confusion and longer use can do nasty things to the liver. The cherries can even cause coma.