1st definition: Scumbunkler is a term used to identify a rat toothed little Judas.
2nd definition: Scumbunkler can also be used to identify someone who is normally quite courteous and fair, but has decided to do something pretty scummy to save them either time or money.
First example:
First guy: “Hey shall we get a train ticket from the machine?”
Scaralambus: “Nah let’s crawl through the sewers, and sneak on. I ain’t paying £3.50”
First guy: “scumbunkler”
Second example:
Pedro: “Howard why are we driving on the pavement? I’m pretty sure we just ran someone over you scumbunkler..”
Peen: “I’m not waiting for that traffic lol. I always drive on the pavement. Most of them survive.”