Depends on the character, but my two favorite methods:
Remnants Power Armor, Slasher, Oh Baby!
(does anyone know if SuperSlam works on them? That character has the perk, but never stopped to actually see if they were falling. Just swung like crazy until they explode)
Or
Boone (for the perk) Brush Gun with handload rounds, and possibly some psycho. If there's a large group of em, switch to Ratslayer with AP rounds and A LOT of distance. So far away that you can't even see them w/o the scope. And slowly plink em down. Very slowly. Changing locations from time to time. Guerilla tactics, whittle them down to nothing.
Or
Q-35 or Holorifle (fully modded) and Max Charge. Always keep a couple dozen Max MFC around, just in case.