frogs also produce venom and only some venom can kill and blindness is also possible

for example - the golden dart poison frog can kill living beings instantly

Poison dart frog skin, like all frogskin, is covered with mucus. In poison dart frogs, the mucus contains poison from the insects it eats, like poisonous ants. When you touch the poison dart frog, this poison touches your skin. It usually causes little more than a red spot and swelling, but it can be worse, especially if it enters your bloodstream through a cut or something. If that's the case, you can get nausea, hallucinations, and all kind of other side effects. The most poisonous frog contains enough poison to kill 50 people, and uses a neurotoxin.
Poison dart frogs have a nerve poison in their skin that causes paralysis. It can enter the blood through wounds and through the pores. Once in the body it starts to paralyze you.

Ingestion is another route of entry. A snake attempting to eat one of these frogs will learn to avoid them if it survives. A collector will learn to wash his hands after handling them, before eating, if he survives.

The toxins in the poison arrow frogs comes from their diet. They concentrate and store alkaloid toxins from the insects they eat. Captive bred frogs that have never had those insects in the diet are not particularly toxic.