Basically it has low damage and armor armor pen but when it hits it massively debuffs consciousness and flatlines your manipulation with a massive AOE with a single hit. While this can result in death easily with 2-3 hits as the poison seems to "pulse" and get more severe then recover then get more severe then recover, it typically receeds in severity within a few in game hours. This is seen with multiple hits, so like 2-3 throws.

As you can see it has a total tend amount, meaning it doesn't go away from being treated and the time between tendings is 1+ days. If you end up with full immunity it is not removed but instead spams the "fully healed" message. And your colonists will stay in bed rest the entire time, which is like most of a week even with a good medic.

@Mlie did some dedicated testing with only the grenades mod active.
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3544881551
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3544881783
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3544882017

@Ralathar44 The grenades has not been changed regarding effectiveness as far as I know. Not sure what the issue in your setup could be

The hornet grenade seems to have some excessive effectiveness. I don't remember it being this strong. A single misthrow had multiple colonists in bed for several days building immunity to the venom.

Then when immune it spammed "fully healed". I had to use dev mode to restore the body part to get rid of it in the end.

@Guineatown20806 Not much I can say here. You use it like any other

@DuckGoosebear PrairieDogLover No idea, you would have to ask the original author

Are these based off Worms grenades?