There are claims that the bullet ant is meant to be one of the worst. Though after having a couple stings at different locations in Peru (Once when I got caught in a sudden storm, and had to crawl through broken bamboo to get back, and another when moth sheeting), I was generally underwhelmed. Like it was pretty good, but compared to eating something like carolina reaper mash, dunno. Like it stung for a day, and was itchy for several more.
On a spot basis, I feel the stings I had in the same regions from Apoica (Night flying paper wasps) stung a lot more, but also tended to go away a lot quicker (Like within the hour).
That time about seven years back I accidently slid over a european/german ground wasp nest when sliding down a bank https://i.imgur.com/UG3Tgid.jpg (Warning topless male shot). Was concerning since many of them went up my top, and didnt seem happy about it. Because I was about 2 hours into a 5 hours drive, I was quite cautious the rest of the way, in case my body decided to over react. Luckily it wasnt too bad.
About 11 years ago, I accidently crashed my car through a farm fence post, when I had a blow out on gravel. I reported it to the farmer, and got a dog bite (The farmer wasnt home). That took a bit of flesh, but wasnt too bad.
The only snakes I have been biten by are a eastern king, and a milk snake, both were fine. The only spiders are a whitetail and a uliodon. Both were fine.
I am not the biggest fan of being covered in leeches. Had that a few times, the bite dosent hurt, but the bleeding for a couple hours is tedious.
I often work with https://www.inaturalist.org/observations/65734464westland petrels. Mostly juves, which dont bite much. But helping in the colony, the adults really can. One day, I failed to ācontrol the headā whilst my colleague was doing measure meants, and it managed to latch onto my nipple through my tee. That wasnt great.
When it comes to pain, I feel this plant is worse than most stings I have had, including the bullet ant/wasps. https://en.wikipedia.org/wiki/Urtica_ferox