Narrow Escape: After setting off the timer in the Necrum Mines Ender, go back and pull the electricity lever again before you leave
I'm annoyed you can't slap flying sligs, that could have been a good achievement
EDIT: Closest I've got to 3 scrab fight is to possess a scrab and stand exactly between two other scrabs, then time your spin attack to when they start fighting, they'll finish their fight then the winner will die instantly