I'm the same way about possums and groundhogs, after the damned things tore out abut 20 feet of heating/cooling ductwork under my house. Found the damned possum INSIDE one of the pipes! I kill any and all of them every chance I can. No mercy, no prisoners!
LOL! I get possums under my house all the time too. I bought me some rat traps and sometime it kills them outright and sometimes it don't. If it don't though it gives them one heck of a headache and they usually end up dying a couple days lays later... usually at the farthest point under my house from the access hole.

Nothing and I mean nothing smells worse than a dead possum that is really ripe.
I live about 150 yds from the river and we get all kinds of critters and I kill them all.
