Colossal Squid tentacles
For comparison's sake
I've always been fascinated by the Irukandji Jellyfish
Its venom is very powerful, 100 times as potent as that of a cobra and 1,000 times as potent as that of a tarantula. Symptoms from a small amount of venom include severe pains at various parts of the body (typically excruciating muscle cramps in the arms and legs, severe pain in the back and kidneys, a burning sensation of the skin and face), headaches, nausea, restlessness, sweating, vomiting, an increase in heart rate and blood pressure, and psychological phenomena such as the feeling of impending doom. These can last from hours to weeks and generally require hospitalization.
And here's how big this beast of an animal is: